| Telaware | North Yorkshire |
| Telcheck | Surrey |
| Telcom Networks Ltd | |
| Tele-Products Ltd | North Yorkshire |
| Telecetera Ltd | Worcestershire |
| Telecom 2000 Ltd | Dorset |
| Telecom Care Ltd | Nottinghamshire |
| Telecom Connections Ltd | Nottinghamshire |
| Telecom Green Ltd | County Durham |
| Telecom Midlands | |
| Telecom Networks | |
| Telecom Plus plc | |
| Telecom Services & Maintenance Ltd | West Sussex |
| Telecom Solutions & Services | Worcestershire |
| Telecom Spares Ltd | Hertfordshire |
| Telecom TV | Oxfordshire |
| Telecommunications Software Engineering | Cumbria |
| Telecoms Jobsource | Hampshire |
| Telecoms World plc | Greater London |
| Telecoms.com | Greater London |
| TeleData UK Ltd | Hampshire |
| Teledyne e2v | |
| Telefónica O2 UK Ltd | Berkshire |
| Telefónica Tech UK Ltd | Greater London |
| Telekinetix Ltd | Bedfordshire |
| telent Technology Services Ltd | Warwickshire |
| Teleplan Forsberg Ltd | |
| TeleRetro | |
| Telescope Analytics | |
| Telescope Holdings Ltd | |
| Telescopic | |
| Telesgop | |
| Telesoft Technologies Ltd | Dorset |
| Telet Research (N.I.) Ltd | |
| Televagal | |
| TellJO Ltd | East Sussex |
| Tellow Fly Design | Conwy |
| Telos | Greater London |
| Telsa Media | |
| Teltech Communications | Warwickshire |
| Tematic Ltd | Cambridgeshire |
| Temin | |
| Template Studio UK Ltd | Buckinghamshire |
| Temple Kinght plc | Kent |
| Tempora Software | Kent |
| Temporall | |
| Temporis Capital Ltd | |
| Tempus Computers Ltd | West Midlands |
| Ten 4 Design | |
| Ten Ten Systems | Cheshire |