Top 20 Custom Software Development Companies in London

London’s tech scene is booming, and custom software can give businesses a crucial edge. From bespoke enterprise platforms to mobile apps, the city’s developers cover every need. Below is our curated list of the Top 20 custom software development companies in London. Each entry includes their core services, team size, typical pricing, standout projects, and pros and cons. We've sourced reliable profiles and reviews for accuracy. Each listing ends with a clear call-to-action (CTA) so you can easily reach out to the firm.

1. Empyreal Infotech – Wembley (London, UK)

Empyreal Infotech is a Wembley-based software agency offering end-to-end custom solutions. Their services span website development, mobile apps, e-commerce sites, CRM/ERP systems, SEO, and digital branding. Empyreal emphasizes fast delivery and transparent pricing: they claim a “Quick Turn Around Time”, 24/7 availability, and flat rates for projects. They tout a team of 50+ in-house developers (SoftwareWorld lists “10–49 employees,” but their site indicates 50+). Despite this mid-size team, Empyreal has built varied projects (e.g., an online sports platform Luca and a financial events portal).

1. Services: Custom web & mobile apps, ecommerce, CRM/ERP integrations, UI/UX design, SEO.
2. Team Size: ~50 in-house developers.
3. Pricing: Very affordable (hourly rate <$25; small projects under $5K).
4. Notable Projects: Launched “Luca” sports gaming platform and a financial events analytics portal (from their portfolio).
5. Pros: 24/7 support and flat-rate fees; quick turnaround; broad services for startups.
6. Cons: Smaller agencies may lack specialized staff for very large enterprise projects; limited publicly documented case studies.
7. CTA: Visit Empyreal Infotech to request a quote or portfolio examples.

2. Unified Infotech – London, UK

Unified Infotech is an award-winning custom software development firm (founded in 2010) with a London presence. They offer web, mobile, SaaS, IoT, blockchain and cloud engineering services. GoodFirms notes their “award-winning” 14-year track record and lists them as a top custom software partner. Unified's global team is around 250+ employees (with 105+ in engineering), giving them the scale to handle large projects. They usually target mid-to-enterprise budgets; GoodFirms shows rates of $50–$99/hr. Notably, Unified has delivered complex SaaS platforms (e.g., modernizing a NASDAQ-listed law firm’s AI transcription service and building a patented multi-site recording SaaS). Their Clutch rating is ~4.6/5.

1. Services: Enterprise software, SaaS platforms, mobile apps, cloud consulting, AI/ML and IoT solutions.

2. Team Size: ~250 employees globally.

3. Pricing: Mid-range rates ($50–$99/hr); typical project budgets starting $50K+.

4. Notable Projects: Developed an AI-driven transcription SaaS for a Nasdaq firm; built a multimillion-dollar patented recording/analytics SaaS.

5. Pros: Deep enterprise/SaaS expertise; strong track record (1,200+ clients and Fortune 500 projects); high-quality engineering (Clutch 4.6/5).

6. Cons: Based in the US/India (HQ in NYC); may be pricier and less agile than smaller London startups.

7. CTA: Visit Unified Infotech for case studies or to request a consultation.

3. Goji Labs – London, UK

Goji Labs is a London-based digital product agency focused on UX-driven mobile and web apps. They brand themselves as “Building It Right the First Time”, emphasizing strategy, UX and clean code. DesignRush notes they have under 50 employees, a 5.0 rating, and charge about $149/hr (projects often $25K–$50K). In practice, Goji's small team (≈30–40 devs) specializes in end-to-end product development: from strategy and prototyping to design and development. Their portfolio includes high-impact apps (e.g., a social sports gaming app “AngelFire” and AI hardware integration Kabata).

1. Services: Mobile & web application development, product strategy, UX/UI design, MVP and prototyping services.
2. Team Size: < 50 employees (small, cross-functional teams).
3. Pricing: ~$149/hr (as per DesignRush); typical project budgets $25K–$50K.
4. Notable Projects: Developed an athlete-stock-exchange platform (PredictionStrike) and an AI-powered fitness device app, driving significant user engagement.
5. Pros: Highly experienced in UX and agile development (5-star design ratings); lean team means personal attention; quick prototyping and MVP focus.

6. Cons: Small size may limit capacity on huge projects; rates are mid-to-high for a boutique ($149/hr).

7. CTA: Check out Goji Labs to view case studies or request a quote.

4. Mercury Development (MercDev) – London, UK

Mercury Development is a long-standing, London-based software firm (23+ years). They offer full-stack development, mobile apps, AI/ML, data science, QA and UI/UX design. With around 400 employees globally (250–499 in the UK office), they have significant scale. DesignRush highlights their “best-in-class” development experience. Mercury typically targets larger projects, charging about $50/hr (very competitive for enterprise scale). They serve big clients across industries, from fintech to e-commerce. Notable work includes a major refinancing platform and integrated IoT solutions.

1. Services: Custom web & mobile development, cloud platforms, AI/ML solutions, Big Data, QA/testing, UI/UX design.

2. Team Size: ~250–499 in London (400+ worldwide).

3. Pricing: ~$50/hr (low relative rate for such a large firm).

4. Notable Projects: Built high-security e-commerce and finance platforms; developed complex data analytics and AI prototypes for large enterprises.

5. Pros: Vast experience (23+ years) and large resources; full-service (design, dev, QA under one roof); affordable rates given size.

6. Cons: Large firms are slower on change requests; bureaucracy can mean less flexibility; brand recognition is stronger in the US.

7. CTA: Learn more and get in touch via MercDev's website.

5. Suffescom Solutions – London, UK

Suffescom Solutions is a mobile-first development agency in London (design award-winner). They focus on mobile app development across industries. Suffescom's team is sizable (around 250–499 members), enabling them to scale quickly. According to DesignRush, they handle medium-sized projects ($10K–$25K) and list rates as “inquire”, suggesting customized quotes per project. Their portfolio spans healthcare, fintech, and social apps. For example, they built a secure telemedicine app and various payment platforms.

1. Services: Mobile app development (iOS/Android/Flutter), web development, UI/UX design, AI/AR integration.

2. Team Size: 250–499 employees globally (London office included).

3. Pricing: Project-based; typical budgets $10K–$25K; exact hourly rates on inquiry.

4. Notable Projects: Developed cross-platform mobile solutions for healthtech startups and collaborative business apps; often include AI features.

5. Pros: Large talent pool for quick scaling; winning focus on mobile innovation; design award-winning capabilities.

6. Cons: Rates and process are custom (no flat pricing); large agency model means smaller clients may receive less priority.

7. CTA: Visit Suffescom Solutions to discuss your mobile app requirements.

6. Codal – Lincoln (serving London)

Codal is a UK-based design and development consultancy (headquartered in Lincoln) with a London presence. They specialize in data-driven strategies and digital transformation. Codal's team is 250–499 people, making them one of the larger players. They offer UX strategy, web/mobile apps, and enterprise solutions. DesignRush notes their emphasis on “cutting-edge, data-driven strategies”. Their rates run around $145/hr, and they handle enterprise-scale budgets (min $50K). Notable work includes retail optimization platforms and financial customer portals.

1. Services: Custom software & web applications, UX/UI design, enterprise portals, DevOps, and digital strategy.

2. Team Size: 250–499 developers and designers.

3. Pricing: ~$145/hr; project minimums typically $50K+.

4. Notable Projects: Created large-scale e-commerce and loyalty platforms; developed complex analytics dashboards for Fortune 500 clients.

5. Pros: Strong design focus with strategic planning; good for midsize-to-large projects; data-driven approach.

6. Cons: Higher rates; Lincoln-based HQ may limit casual London networking (though they do have UK presence); not a budget option for SMBs.

7. CTA: Check Codal's site for client case studies or quote requests.

7. One Beyond – Farnborough (London Region, UK)

One Beyond is an award-winning bespoke software developer based in Farnborough with offices across the UK and Europe. Established in 1994, they have 200+ employees and specialize in Microsoft .NET and Azure solutions, enterprise web/mobile apps, and DevOps. Their expertise includes mission-critical systems for finance, energy, and public sectors. LinkedIn notes they’ve built “intelligent, cost-effective” applications since 1994. They’re a Microsoft Solutions Partner and have won multiple industry awards. One Beyond typically handles large-scale projects (often million-dollar budgets).

1. Services: Enterprise web & mobile apps, cloud/DevOps (Azure/AWS), data platforms, digital transformation consulting.

2. Team Size: 200+ developers and consultants.

3. Pricing: Enterprise-level rates (often fixed-bid); detailed quotes on request.

4. Notable Projects: Designed a real-time trading platform for asset management and complex operational systems for logistics firms.

5. Pros: Deep enterprise and Microsoft expertise; multi-award winning quality; stable and mature processes; “200+” staff for reliability.

6. Cons: Geared toward large corporations (min budget often high); slower onboarding for small projects; old-school culture might not suit all clients.

7. CTA: Learn more at One Beyond or request a consultation.

8. Apadmi – Manchester/London, UK

Apadmi is a top UK digital agency (HQ in Manchester) known for mobile-first solutions. They have 300+ specialists (now ~450 after a merger) across Manchester, London, Edinburgh, and Europe. Apadmi excels in enterprise mobile apps, IoT, AR/VR and UX design. On LinkedIn, they list clients like Domino’s, Co-op, NHS and TalkTalk. Their services include strategy, full-stack development, and 24/7 support. Given their calibre, rates are premium (often $150+/hr for enterprise work).

1. Services: Mobile app development, IoT/AR/VR apps, UX/UI design, enterprise integration, strategy consulting.

2. Team Size: 300+ (now ~450) mobile/tech experts.

3. Pricing: High-end (enterprise rates, likely $100–$200/hr).

4. Notable Projects: Built a UK-wide mobile ordering app for Domino’s; developed AR driving simulator for insurance (Root); healthcare apps for NHS.

5. Pros: Extensive app dev experience; large, specialist team; proven process for big brands; European presence.

6. Cons: Premium pricing and focus on large clients; slower turnaround due to size; may not suit very small projects.

7. CTA: Explore Apadmi's portfolio and contact them via Apadmi's site.

9. Bit Zesty – London, UK

Bit Zesty is a London-based innovation agency focused on product strategy and web app development. They are a small team (11–50 people) with strong UX/UI skills. Their specialties include Ruby on Rails, React, and Elixir. Bit Zesty has a 4.8/5 rating on The Manifest and Clutch. Clients praise their flexibility and end-to-end delivery. Clutch notes they handle projects >$25K with rates $150–$199/hr. An example project: modernizing an online video tool platform and integrating e-commerce and reporting features.

1. Services: Product strategy, UX/UI design, web application development, full-stack engineering (RoR, JavaScript frameworks).

2. Team Size: ~11–50 employees.

3. Pricing: Premium boutique rates (~$150–$199/hr); typical project min $25K.

4. Notable Projects: Revamped a video platform’s technology stack, adding analytics and ecommerce; designed enterprise web apps for startups and NGOs.

5. Pros: Boutique agency with high-touch service and strong UX focus; consistent 5-star reviews; quick and agile.

6. Cons: Very small team (limited capacity); higher hourly rates; best suited for mid-sized to large projects.

7. CTA: Visit Bit Zesty to view their case studies or set up a meeting.

10. Zazz – London, UK

Zazz is a veteran London-based software engineering partner, specializing in secure enterprise solutions. They have a large team (250–499) and focus on high-stakes projects (security, compliance). Their tagline is “Modern IT. Built Secure. Typical rates are $45/hr, unusually low, indicating offshore capabilities or blended teams. Clients include large enterprises needing custom IT & DevOps. Zazz has 5-star reviews and solves legacy modernization and cybersecurity challenges.

1. Services: Custom software development, enterprise systems, cybersecurity and penetration testing, IT staffing and support.

2. Team Size: 250–499 engineers and security experts.

3. Pricing: $45/hr (very competitive for enterprise work).

4. Notable Projects: Securing and migrating legacy banking systems; building high-throughput B2B Ecommerce platforms; cloud infrastructure for public sector.

5. Pros: Specialized in security-focused, enterprise-grade solutions; large bench strength; extremely cost-effective rates.

6. Cons: Primarily technical focus (less on design or UX); low rates may hint at offshore work model; marketing and brand are less known.

7. CTA: Find more about Zazz and their IT security services on their website.

11. TRIARE – London, UK

TRIARE is a mid-sized London software house (50–99 employees) that covers the full software lifecycle. They offer web/mobile app development, UI/UX design, prototyping and business analysis. With $45/hr rates, TRIARE is affordable for SMEs. They’ve built SaaS platforms and mobile apps, and emphasize DevOps and API integrations. Clients note their comprehensive approach (“entire development lifecycle”). For example, they developed a CRM platform with a rich UI, and a native mobile app for hospitality.

1. Services: Full-stack custom development (web & mobile), UI/UX design, prototyping, QA/testing, DevOps.

2. Team Size: 50–99 professionals.

3. Pricing: ~$45/hr; flexible models (T&M or fixed).

4. Notable Projects: Delivered a subscription-based SaaS for automotive SMEs; launched cross-platform mobile ordering apps.

5. Pros: Covers all phases of development; nimble team size; good for mid-level budgets; strong in cloud-based solutions.

6. Cons: Smaller companies may lack very deep niche expertise; fewer international clients; not as well known brands.

7. CTA: Contact TRIARE to discuss custom web or app development.

12. Altar.io – London, UK

Altar.io is a boutique London-based product and software development company founded by ex-startup founders. They have under 50 staff and specialize in building digital products from scratch. Their projects focus on product-market fit and launch: they help take ideas from concept to MVP to full release. According to DesignRush, their rate is $100/hr (project budgets $10K–$25K). They’ve created successful apps for fintech startups and consumer platforms, leveraging their entrepreneurial background.

1. Services: Custom software and product development, MVP creation, UX/UI design, startup/scale-up consulting.

2. Team Size: Under 50 (small, cross-functional team).

3. Pricing: ~$100/hr; mid-range project budgets $10K–$25K.

4. Notable Projects: Built mobile/web products for early-stage fintech and IoT startups; created market-entry platforms with strong user focus.

5. Pros: Startup mindset and ownership (ex-founders); very agile and collaborative; focus on successful launches.

6. Cons: Small team size (limited capacity for large projects); fewer reviews (newer company); higher per-hour cost relative to team size.

7. CTA: Visit Altar.io to view examples of products they’ve launched.

13. RootQuotient – London, UK

RootQuotient is a bespoke software and AI development firm, with London offices and co-headquarters in Canada and India. Founded in 2018, their team (50–249 people) delivers machine learning, web and mobile solutions. They earned a 5-star rating on The Manifest with a focus on AI and custom development. For example, they built an AI-driven legal transcript platform and a medical image analysis tool. Services include AI/ML, computer vision, and custom enterprise apps. Their rate is about $100–$150/hr.

1. Services: AI & ML development, computer vision, custom web/mobile apps, IoT integrations.

2. Team Size: 50–249 (multinational team in UK, India, Canada).

3. Pricing: ~$100–$150/hr; project quotes on a case-by-case basis.

4. Notable Projects: Modernized an AI transcription system for legal services; deployed machine learning pipelines for healthcare analytics.

5. Pros: Strong AI/ML expertise; flexible global delivery (multi-country team); startup-like agility.

6. Cons: Mid-sized (may lack bandwidth of larger firms); less name recognition; relatively young company (2018).

7. CTA: Learn more about RootQuotient and their AI development offerings.

14. Vega IT – London / Novi Sad (UK/Serbia/USA)

Vega IT is a mid-size software company (250–999 staff) headquartered in Serbia with London and New York offices. Established in 2008, they provide custom software, CRM integration, e-commerce, and mobile apps. Vega IT serves global clients and offers full-cycle product development. Typical projects start at $10K+. They have built ERP systems and B2B platforms, often for logistics and e-commerce. Their size allows robust support.

1. Services: Custom software and SaaS development, CRM/SI (Salesforce, MS Dynamics), mobile apps, cloud solutions.

2. Team Size: 250–999 (large international team).

3. Pricing: Moderate – project minimum $10K (per The Manifest).

4. Notable Projects: Developed integrated ERP/CRM for freight companies; built cross-platform mobile sales apps; and e-commerce platforms.

5. Pros: Global delivery model; broad industry experience; strong Eastern European talent pool.

6. Cons: UK presence is through an office (main tech teams overseas); communication must be well managed across time zones; not focused exclusively on the London market.

7. CTA: Connect with Vega IT for enterprise development and CRM integration.

15. Andersen Inc. – London, UK (US-UK offices)

Andersen Inc. is a Dallas-based custom software firm with a significant London office. Launched in 2007, they now have thousands of engineers (1,000–9,999). Andersen offers full-service development: custom apps, managed IT, mobile, and consulting. Their high-end clients include Samsung and others. They typically handle very large projects (min budgets $50K+, with teams of 10+). For example, Andersen built a global communication platform for a Fortune 100 company.

1. Services: Custom software development, IT managed services, mobile app development, digital transformation consulting.

2. Team Size: 1,000–9,999 (large global workforce).

3. Pricing: Enterprise-level (likely $150–$200+/hr); projects usually $50K+.

4. Notable Projects: Large-scale web portals and legacy system migrations for Fortune 500 clients; IoT platforms for industrial automation.

5. Pros: Massive resources and broad expertise; strong track record with complex enterprise projects; 24/7 global delivery.

6. Cons: Very high cost; least agile (big-company bureaucracy); focus on long-term contracts (not ideal for SMEs).

7. CTA: Explore Andersen Lab for info on their global dev teams.

16. Future Processing – London/Poland/Ukraine

Future Processing is a Polish-heritage software company (founded in 2000) with an office in London. It has a midsize team (250–999 employees) across Poland, Ukraine, and the UK. They provide custom software development, cloud migration, BI/big data, and QA. They often work on large-scale systems in banking and fintech. For example, they built a real-time trading platform and upgraded a bank’s core systems. Rates are moderate (~$40–$60/hr); the London office enables close client collaboration.

1. Services: Custom software, cloud consulting/migration, big data/BI, QA/testing, enterprise Java/.NET development.

2. Team Size: 250–999 across Eastern Europe and London.

3. Pricing: Mid-range (around $40–$60/hr); project quotes on request.

4. Notable Projects: Developed core banking modules; created complex data analytics pipelines for energy and finance sectors.

5. Pros: Strong Eastern European dev expertise; London presence for local support; extensive tech breadth (BI, cloud, custom).

6. Cons: Not solely London-based (major teams offshore); might not be as visible to London clients as local agencies; communications must bridge multiple countries.

7. CTA: Visit Future Processing for case studies on cloud and software engineering.

17. Imaginary Cloud – London/Portugal

Imaginary Cloud is a software development and design company with offices in London, Portugal and the US. They are a mid-size agency (50–249 people) focusing on web, mobile and AI applications. Over 11 years, they’ve launched 300+ apps, from startups to enterprises. Their clients include Nokia and BBC, and their services cover full-stack development, AI/ML, and UX/UI design. They emphasize agile processes and have won awards for innovation. Projects range from enterprise dashboards to consumer mobile apps.

1. Services: Web and mobile app development, AI/Machine Learning solutions, UX/UI design, AR/VR, and QA.

2. Team Size: 50–249 (multi-office team).

3.  Pricing: ~$60–$100/hr (equivalent to Europe/U.K. mid-tier); project quotes on demand.

4. Notable Projects: Built a multinational e-commerce site with AI recommendations; created AR visualization tools for property development.

5. Pros: Full-stack capabilities with a creative design focus; international presence (client support in local times); agile and innovative culture.

6. Cons: Smaller mid-market focus (not for extremely large systems); primarily headquartered outside the UK (Lisbon), so the “London” office is smaller.

7. CTA: Check out Imaginary Cloud to see their award-winning apps.

18. Infinum – London (HQ San Francisco)

Infinum is an international software development company (50+ team) headquartered in San Francisco, with a London branch. They specialize in mobile and web development for mid-to-large clients. Infinum has a balanced skill set (Android/iOS, .NET, PHP, etc.) and years of experience. Clients include Philips and Cabify. They are known for mobile apps and responsive web design. The Manifest lists them as 4.8/5, with projects of $25K+.

1. Services: Mobile app development, web app development, UX/UI, product strategy, maintenance.

2. Team Size: 50+ (international team).

3. Pricing: Mid-range ($60–$120/hr); typical projects start $25K+.

4. Notable Projects: Developed mobile apps for healthcare, industrial, and retail clients; digital transformation projects for enterprise firms.

5. Pros: Well-rounded technical expertise; boutique feel with mid-sized reliability; strong focus on mobile and user experience.

6. Cons: US HQ means the London team is limited; not UK-native (though they have local project managers).

7. CTA: Visit Infinum to connect with their London office.

19. Kellton Tech – London (Reston, VA HQ)

Kellton is a global IT services firm with an office in London (originally founded in 2009 in Virginia). It’s a very large company (1,000–9,999 employees). Kellton offers custom software development, AI, BI/big data, and mobile apps. They focus on enterprise digitalization. Projects include ERP implementations and AI-driven analytics for banking. With large teams, they handle multi-million-dollar contracts. For example, Kellton developed a business intelligence platform for retail chains.

1. Services: Custom enterprise software, mobile apps, AI & ML solutions, data analytics/BI, cloud services.

2. Team Size: 1,000–9,999 (thousands globally).

3. Pricing: Enterprise rates (likely $150–$200+/hr); big-ticket project budgets.

4. Notable Projects: Built large-scale BI systems for retailers; mobile CRM apps for corporate sales teams; full-suite ERP migrations.

5. Pros: Immense capacity for any scale; comprehensive services including consulting and support; global delivery.

6. Cons: Highest cost structure; not a small business-friendly choice; very corporate.

7. CTA: Learn more at Kellton's site for enterprise digital solutions.

20. AppMakers USA – London, UK (US-based firm)

AppMakers USA is a US-origin company with a London office, offering mobile and web app development. They build cross-platform solutions (the “iOS & Android for the price of one” model). Their London team is small (<50 people), which makes them agile. They handle projects in the $10K–$25K range, suitable for startups and SMEs. Past work includes mobile e-commerce apps and game apps.

1. Services: Mobile app development (iOS/Android/Flutter), website development, backend and API services.

2. Team Size: Under 50 developers in London.

3.  Pricing: Project budgets $10K–$25K; hourly rate on inquiry.

4. Notable Projects: Developed a multi-platform retail app; delivered bespoke enterprise utility apps.

5. Pros: Quick turnaround for small to mid projects; experienced in both Western and UK markets; cost-effective for SME budgets.

6. Cons: Lesser-known brand in the UK; smaller firm (risks on very large projects); support depends on US-London coordination.

CTA: Contact AppMakers to discuss your cross-platform app development needs.