| Syntax Ltd | |
| Syntechnologies | |
| Syntesia Ltd | |
| Synthace | Greater London |
| Synthesis | |
| Synthesis Capital | |
| Synthesis IT | Tyne and Wear |
| Synthesized Ltd | Greater London |
| Synthesized Ltd | |
| SyntheSys | |
| Synthetic Gestalt | |
| Syntony (Search & Selection) Ltd | Kent |
| Syplex Ltd | Cambridgeshire |
| Syrona Health Ltd | |
| Syrris Ltd | |
| Sys-Teams Ltd | |
| SYS3 | Essex |
| Syscom plc | West Midlands |
| Syscomm | West Midlands |
| Sysero | Kent |
| SysFix IT Support Ltd | |
| SysGroup | |
| Sysnet | Glasgow |
| SYSOP Ltd | Greater Manchester |
| Syspec Ltd | |
| Systango | |
| Systec Services Ltd | Bristol |
| Systech Technologies | |
| System 3 Business Solutions | Norfolk |
| System 3 Internet | South Yorkshire |
| System Bookings | |
| System C | Kent |
| System Devices Ltd | Cheshire |
| System Force IT | Gloucestershire |
| System I.T. | Cumbria |
| System Insight | Hampshire |
| System Potential | Cumbria |
| System Q Ltd | Derbyshire |
| System Recruitment Ltd | |
| System Restore UK | |
| System Selection | |
| System Simulation | Greater London |
| System Wise | Edinburgh |
| System:Solutions | |
| Systemactive Ltd | East Sussex |
| Systemagic Ltd | Wiltshire |
| Systematic-ICT | Greater London |
| Systematics Software Ltd | Buckinghamshire |
| Systematix Ltd | Berkshire |
| SystemCore Ltd | Surrey |