This list contains large to mid-sized managed service providers based in London, primarily in IT services and telecommunications. Key players include Vodafone Business, offering mobile, fixed, unified communications, and IoT services, and Colt Technology Services, a global digital infrastructure provider. Other notable companies are Infobip, specializing in omnichannel engagement, and Claranet, a technology services provider in Cloud, Networks, Cyber Security, and Workplace technologies. Gamma supplies Unified Communications services.
The data shows a concentration of companies founded between the mid-1990s and early 2000s, such as Colt Technology Services (1992), Claranet (1996), and Gamma (2002). Several companies also focus on global service delivery, like NSC Global, which provides IT services to clients in over 180 countries, and NTT Global Data Centers, offering reliable data centers worldwide.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 |
Vodafone Businessvodafone.com
Providing mobile, fixed, unified communications, IoT, cloud, and security services to businesses globally, regionally, and locally. |
8,100 | |||
| 2 |
Colt Technology Servicescolt.net
Global digital infrastructure provider connecting businesses across 40+ countries with extensive networks, customer-focused innovation, and reliable connectivity solutions. |
5,107 | |||
| 3 |
Infobipinfobip.com
Global leader in omnichannel engagement, providing messaging tools and solutions for customer engagement, authentication, and security with a strong focus on quality engineering |
3,501 | |||
| 4 |
Claranetclaranet.com
A global technology services provider offering managed services, professional services, and training in Cloud, Networks, Cyber Security, and Workplace technologies since 1996 |
3,073 | |||
| 5 |
Gammagammagroup.co
Gamma is a leading supplier of Unified Communications services in the UK, Germany, Spain, and Benelux, offering robust solutions for communication and collaboration |
2,588 | |||
| 6 |
NTT Global Data Centersservices.global.ntt
Global Data Centers, now a part of NTT DATA, offers neutral access to cloud providers, internet exchanges, and telecom providers with reliable data centers worldwide |
2,449 | |||
| 7 |
Canonicalcanonical.com
Publishing Ubuntu, popular enterprise Linux, open source delivery, cloud to edge, secure, cost-effective, global community, developer platform, remote-first company. |
2,001 | |||
| 8 | 1,442 | ||||
| 9 |
Connectweconnect.tech
Communication experts providing solutions in Contact Centre, Unified Communications, and Network Services, delivering digital transformation through bespoke strategies for businesses globally |
1,387 | |||
| 10 |
Advania UKadvania.co.uk
Specializes in Microsoft technologies like AI, Azure, and Dynamics 365 to deliver transformational IT services and sustainable value for customers. |
1,351 | |||
| 11 |
NSC Globalnscglobal.com
This company simplifies global business with expert teams delivering IT services to clients in over 180 countries, flexibly adapting to their needs |
1,070 | |||
| 12 |
Maintelmaintel.co.uk
Provider of cloud communications and managed services, specializing in digital transformation for public and private sectors Delivering digital workplace, customer experience, and secure connectivity solutions globally |
946 | |||
| 13 |
EXA Infrastructureexainfra.net
A leading digital infrastructure platform in Europe and North America, owning a vast fibre network, data centers, and sub-sea routes for optimal connectivity |
846 | |||
| 14 |
Cobraamazingsupport.co.uk
We successfully completed a company acquisition in June 2012 resulting in a re-brand to Amazing Support, providing quality business solutions |
831 | |||
| 15 | 782 | ||||
Want more companies than this list?This page shows the largest ones only. Connect to Tamtam to see every company that matches, filter by size, industry or growth, and reach their decision-makers. | |||||
| 16 | 752 | ||||
| 17 | 706 | ||||
| 18 |
Exponential-eexponential-e.com
Provides superfast network and cloud infrastructure delivering tailored enterprise solutions including data centre, cloud, unified communications, security, and IT services. |
695 | |||
| 19 |
Zenzerozenzero.co.uk
Design tailored IT infrastructure solutions using proven technologies to optimize client operations and maximize value from resources. |
688 | |||
| 20 | 679 | ||||
| 21 |
Onneconnecgroup.com
A leading technology partner offering end-to-end connectivity solutions including structured cabling, networking, managed services, and integrated intelligent systems for businesses globally |
665 | |||
| 22 |
Options Technologyoptions-it.com
Provides global financial technology solutions specializing in banking and trading infrastructure, integrating high-performance networking, cloud, security, and AI technologies. |
641 | |||
| 23 |
Giacomgiacom.com
The company provides a platform for technology resellers and MSPs to access various services and products to create solutions for UK small businesses |
633 | |||
| 24 |
Nscalenscale.com
Specializing in AI, Nscale provides a GPU cloud platform in Europe for high-performance computing optimized for training and intensive workloads |
585 | |||
| 25 |
Telef贸nica Tech (EN)telefonicatech.uk
Specialist provider of integrated technology solutions including cybersecurity, cloud, data, AI, business applications, and digital workplace services. |
557 | |||
| 26 |
Fortray Global Service Limitedfortray.com
Provides services for digital transformation, cybersecurity, cloud, and managed IT. Also develops talent through tech and AI bootcamps for various digital skills. |
547 | |||
| 27 |
Colt Data Centre Servicescoltdatacentres.net
Specializing in data centre services, the company designs, builds, manages, and innovates infrastructure solutions to support customers' growth globally |
483 | |||
| 28 |
Hitachi Solutions UKhitachi-solutions.co.uk
Provides business-tailored services and solutions for transformation journeys, including finance, low code, AI, and data-based transformation, offering advisory and application support. |
462 | |||
| 29 |
Global Switchglobalswitch.com
Ownership and operation of large-scale, carrier-neutral data centers across Europe and Asia-Pacific, providing secure, resilient solutions to diverse customers. |
447 | |||
| 30 |
Easynet Groupeasynet.com
A provider of managed services for national and global businesses, offering network, hosting, and unified communications solutions, along with security and application performance management |
408 | |||
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How this list is built
Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 12, 2026.
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