| Celllife U.K. Limited | Seaford | 1978 |
| Cellment Ltd | London | 2024 |
| Cello Service Ltd | Hamilton | 2012 |
| Celloglas Leicester Limited | Leicester | 2024 |
| Celloglas Mirri Limited | Reading | 2024 |
| Celloglas Scotland Limited | Glasgow | 2025 |
| Cellord Group Limited | Cardiff | 2019 |
| Cellpath Limited | Altrincham | 1984 |
| Cellroe Ltd | London | 2022 |
| Cellseco Limited | Salisbury | 2010 |
| Cellspex Ltd | Northampton | 2024 |
| Cellsway Limited | Palmers Green | 2020 |
| Cellular Agriculture Ltd | Llanelli | 2016 |
| Cellular Mouldings Limited | Corby | 1994 |
| Cellular Services Limited | Wokingham | 1986 |
| Cellularity Limited | London | 2005 |
| Cellustar Company Limited | Cheltenham | 1992 |
| Cellvital AI Ltd | Surbiton | 2026 |
| Celnovit Ltd | London | 2023 |
| Celosia -RE Ltd | Mitcham | 2021 |
| Celox Medical Limited | Crewe | 2017 |
| Celox PPH Limited | Crewe | 2022 |
| Celoxica Holdings Limited | London | 1999 |
| Celoxica Limited | London | 1996 |
| Cels Contracts Limited | Dover | 2014 |
| Celsis Group Limited | Margate | 2010 |
| Celsis Limited | Margate | 1992 |
| Celsius Air Conditioning Services Limited | Greater Manchester | 1991 |
| Celsius Commercial Refrigeration Limited | Farnham | 2022 |
| Celsius Cooling and Heating Ltd | Gloucester | 2018 |
| Celsius Engineering Services Limited | Carlisle | 2010 |
| Celsius GAS & Heating Services Limited | Birmingham | 2011 |
| Celsius Heating Ltd | Surrey | 2007 |
| Celsius Insulation Systems Ltd | Clitheroe | 2024 |
| Celsius.Plumbing Ltd | Stalybridge | 2014 |
| Celt Spirit Limited | Lostwithiel | 2025 |
| Celtech Construction UK Limited | Manchester | 2015 |
| Celtek Calibration Limited | Wigan | 1997 |
| Celtek Electronics Limited | Cheadle | 1989 |
| Celtek Systems Limited | Chorley | 2016 |
| Celtheath Limited | Bourne End | 1990 |
| Celtic Art Limited | East Kilbride | 1980 |
| Celtic Chemicals Limited | Port Talbot | 1979 |
| Celtic Cladding Services Ltd | Llanelli | 2009 |
| Celtic Coast Fish Company Limited | Llanelli | 2016 |
| Celtic Cocoa Ltd | Glasgow | 2023 |
| Celtic Coffins Limited | Treorchy | 2003 |
| Celtic Composites Ltd | Swansea | 2012 |
| Celtic Concrete Ltd | Crosshands | 2016 |
| Celtic Cooling Limited | Llanrwst | 2008 |
| Celtic Country Wines Limited | Llandysul | 2020 |
| Celtic Craft Carpentry Limited | Ammanford | 2025 |
| Celtic Cross Joinery Limited | Penzance | 2006 |
| Celtic Doors Ltd. | Pontyclun | 2012 |
| Celtic Fencing Services Limited | Cardiff | 2024 |
| Celtic Forge Ltd | Carmarthen | 2016 |
| Celtic Granite Solutions Limited | Bristol | 2015 |
| Celtic Heat Packs Ltd | Pwllheli | 2024 |
| Celtic Heritage Reclaimed Stone Products Ltd | Pwllheli | 2025 |
| Celtic Hives Limited | Aberdeen | 2025 |
| Celtic Horizons Limited | Caerphilly | 2011 |
| Celtic Instrumentation Ltd | Llanelli | 1995 |
| Celtic Intuition Limited | London | 1994 |
| Celtic Iron Limited | Ammanford | 2019 |
| Celtic Kilncare Limited | Newport | 1992 |
| Celtic Liquid Screed Ltd | Crosshands | 2016 |
| Celtic Machines Ltd | Cowbridge | 2008 |
| Celtic Marches Beverages Ltd | Bromsgrove | 2010 |
| Celtic Minerals Limited | Cardiff | 2022 |
| Celtic Nature Group Limited | London | 2018 |
| Celtic Oak Flooring Limited | Llanelli | 2015 |
| Celtic Oriental Holdings Limited | Hengoed | 2026 |
| Celtic Oriental Limited | Hengoed | 2010 |
| Celtic Precision Ltd | Swansea | 2022 |
| Celtic Prints Limited | Aberdeen | 2025 |
| Celtic Process Systems Limited | Whitland | 2003 |
| Celtic Property Maintenance Services Limited | Cardiff | 2010 |
| Celtic Ready MIX Limited | Llanelli | 2009 |
| Celtic Reflections Limited | Newcastle Emlyn | 2000 |
| Celtic Renewables Grangemouth Limited | Edinburgh | 2017 |
| Celtic Renewables Limited | Edinburgh | 2011 |
| Celtic Security Solutions Ltd | Newquay | 2025 |
| Celtic Services Ltd | South Yorkshire | 2005 |
| Celtic Spirit Co. (Anglesey) Limited | Holyhead | 2019 |
| Celtic Stone NW Limited | Mold | 2025 |
| Celtic Terahertz Technology Limited | Chepstow | 2022 |
| Celtic Upvc Ltd | Llanelli | 2022 |
| Celtic Wellbeing Ltd | Conwy | 2011 |
| Celtica Foods Limited | Llanelli | 2002 |
| Celtictech Ltd | Helston | 2015 |
| Celtis Design Ltd | Enfield | 2024 |
| Celtlec Electrical Ltd | Newport | 2023 |
| Celtone Musical Instruments Ltd | Belfast | 2023 |
| Celtrack Installation Services Ltd | Weston Super Mare | 2010 |
| Celuaris Limited | Cardiff | 2017 |
| Celugreen Technologies UK Ltd | Rochester | 2024 |
| Celurca Stonemasonry Ltd | Brechin | 2025 |
| CEM Automation Ltd | Magherafelt | 2025 |
| CEM Eltutar Motors Limited | London | 2025 |
| CEM Jewellery Ltd | London | 2025 |