| 3C Buildings RTM Company Limited | London | 2008 |
| 3C Business Associates Limited | Stonehouse | 2003 |
| 3C Business Solutions Limited | Havant | 2014 |
| 3C Capital Partners Ltd | London | 2022 |
| 3C Construction Cost Consultants Limited | Glasgow | 2019 |
| 3C Consultancy Services Ltd | Exeter | 2019 |
| 3C Design Partnership Limited | Milton Keynes | 2004 |
| 3C Education and Research CIC | London | 2024 |
| 3C Films Limited | London | 2006 |
| 3C Global Ltd | London | 2015 |
| 3C Global-Pi Ltd | London | 2015 |
| 3C Global-Se Ltd | London | 2015 |
| 3C Interiors Ltd | Grimsby | 2018 |
| 3C Interiors Workplace Design Ltd | Amersham | 2023 |
| 3C Legal Limited | Tewkesbury | 2017 |
| 3C Legal Services Ltd | London | 2007 |
| 3C Legal Wills & Probate Ltd | Worcester | 2026 |
| 3C Marine Ltd | Derby | 2014 |
| 3C Marketing Limited | Cheltenham | 2016 |
| 3C Media Ltd | Lancing | 2014 |
| 3C Media Solutions Limited | Romney Marsh | 2015 |
| 3C PAY Ltd | London | 2025 |
| 3C Petcu Limited | Nottingham | 2024 |
| 3C PR Limited | Manchester | 2014 |
| 3C Solutions Limited | Walsall | 2016 |
| 3C Strategic Ltd | Grimsby | 2016 |
| 3C Test Limited | Silverstone, Towcester | 1996 |
| 3C Venture Capital Ltd | Leeds | 2021 |
| 3CA Limited | Kendal | 2006 |
| 3CAP Consulting Limited | Edinburgh | 2009 |
| 3CB Ltd | Newcastle-Under-Lyme | 2020 |
| 3CC Group Limited | Epsom | 2026 |
| 3CC London Limited | Lymington | 2018 |
| 3CF Ltd | Dalgety Bay | 2025 |
| 3CG Consulting Limited | Dungannon | 2022 |
| 3CG Holdings Limited | London | 2016 |
| 3CG Scaffolding Limited | Cardiff | 2019 |
| 3CL (UK) Limited | Gillingham | 1980 |
| 3CN Enterprises Limited | Winchester | 2018 |
| 3CO Consulting Ltd | Heanor | 2026 |
| 3COIL Limited | London | 2018 |
| 3CONSULTANCY Ltd | Abingdon | 2021 |
| 3CORE2 Certification Ltd | Sale | 2019 |
| 3COSYSTEM Ltd | Hinckley | 2025 |
| 3CR Limited | London | 2025 |
| 3CRISK Limited | Nottingham | 2005 |
| 3CROSSFIRE Limited | Poole | 2006 |
| 3CS Consulting Limited | Penrith | 2019 |
| 3CS Corporate Solicitors Limited | London | 2012 |
| 3CS Holdings Limited | London | 2008 |
| 3CS Vectis Ltd | Southampton | 2025 |
| 3CUBED Consultants Ltd | Ruislip | 2022 |
| 3CV Ventures Ltd | London | 2023 |
| 3D 360 Limited | Manchester | 2020 |
| 3D 360 Skills Academy CIC | Manchester | 2023 |
| 3D Accountancy Ltd | Ruthin | 2014 |
| 3D Accountants Ltd | London | 2026 |
| 3D ADM Ltd | Coventry | 2024 |
| 3D Agriculture Limited | Hayes | 2021 |
| 3D Applications Limited | Harrow | 2013 |
| 3D Approach Limited | Abingdon | 2007 |
| 3D at Depth Limited | Great Yarmouth | 2018 |
| 3D Automotive Ltd. | Epsom | 2017 |
| 3D Avionics Ltd | Wokingham | 2017 |
| 3D BIM Limited | Newcastle-Under-Lyme | 2020 |
| 3D BIM Solutions Ltd | High Wycombe | 2018 |
| 3D Building Scans Ltd | Warrington | 2019 |
| 3D CAD & Engineering Ltd | Shildon | 2016 |
| 3D CAD Design Limited | Manchester | 2011 |
| 3D CAD Ltd | Saffron Walden | 1998 |
| 3D CAD Tech Ltd | Hartlepool | 2015 |
| 3D Certhub UK Ltd | London | 2025 |
| 3D Coaching Ltd | Cockfosters | 2003 |
| 3D Coded Limited | Euxton Lane, Chorley | 2019 |
| 3D Complete Solutions Ltd | Newcastle Upon Tyne | 2016 |
| 3D Concept Engineering Ltd | London | 2025 |
| 3D Concepts and Design Limited | Shenley | 2005 |
| 3D Concepts Realised Ltd | Shrewsbuy | 2013 |
| 3D Construct Limited | Leigh-On-Sea | 2014 |
| 3D Consultancy Ltd | Chester | 2025 |
| 3D Craft Hub Ltd | Manchester | 2025 |
| 3D CUT Limited | London | 2013 |
| 3D Design & Planning Ltd | Watford | 2019 |
| 3D Design & Projects Ltd | Manchester | 2025 |
| 3D Design & Solutions Ltd | Long Eaton | 2010 |
| 3D Design and Detail Limited | Leeds | 2001 |
| 3D Design Centre Ltd | Chesterfield | 2021 |
| 3D Design Consultants Ltd. | Dagenham | 2017 |
| 3D Design LAB Ltd | Edinburgh | 2022 |
| 3D Drone Services Ltd | Faversham | 2019 |
| 3D Dynamix Ltd | London | 2023 |
| 3D ENG Ltd. | Glasgow | 2024 |
| 3D Engine Limited | Gillingham | 2015 |
| 3D Engineering Design Limited | Mansfield | 1997 |
| 3D Engineering Global Limited | London | 2018 |
| 3D Engineering Ltd | Gloucestershire | 2007 |
| 3D Engineering Services Ltd | Derby | 2019 |
| 3D Engineering Surveys Limited | Exeter | 2012 |
| 3D European Holdings Limited | Hemel Hempstead | 1990 |
| 3D FD Limited | Bournemouth | 2008 |