| CCS IT Solutions Ltd | |
| CCS Leeds | West Yorkshire |
| CCS Ltd | |
| CCS Media Ltd | Glasgow |
| CcS satcom | Essex |
| CCT Group Ltd | East Riding of Yorkshire |
| CCTV Surveillance Ltd | Cambridgeshire |
| CD2 Solutions | Norfolk |
| CDE Systems Ltd | South Yorkshire |
| CDN77 | |
| CDR Group | Derbyshire |
| CDS | |
| CDS Networks Ltd | |
| CE Engineering (Europe) Ltd | Kent |
| CEE Sourcing Ltd | |
| Ceejay Software Ltd | Falkirk |
| Cefar Ltd | |
| CEI Exhibitions | |
| Cel Stores | Leicestershire |
| Celadon Pharmaceuticals Ltd | |
| Celaton | Buckinghamshire |
| CELCAT | West Midlands |
| Celebro | Essex |
| Celentyx | |
| Celerik | |
| Celestia UK | |
| Celestial | Greater London |
| Celex Oncology Innovations Ltd | |
| Celf Creative | |
| Cell Pack Solutions | Tyne and Wear |
| Cell ProTx Ltd | |
| Cell Software | |
| CelLBxHealth | |
| CellCentric Ltd | |
| Cellesce Ltd | |
| Cellexus | |
| Cellhire plc | North Yorkshire |
| Cellomatics BioSciences Ltd | |
| CellPath Ltd | |
| CellPoint Digital | |
| Cellsway | |
| Cellular Origins Ltd | |
| Cellular Solutions Ltd | Tyne and Wear |
| CellVoyant | |
| CeloApps | |
| Celtic Renewables | |
| CEM Systems | Belfast |
| Cemoc Ltd | Isle of Wight |
| Cenobiologics Ltd | |
| CENSIS | |