| Unecom | Leicestershire |
| Uni-Mail Ltd | Oxfordshire |
| Unibuddy | |
| Unicom Communications | |
| Unicorn Biotechnologies | |
| Unicorn Designers | Suffolk |
| Unicsoft | |
| Unified Business Systems Ltd | Nottinghamshire |
| Unified Software | Tyne and Wear |
| Unified World Communications | Lancashire |
| Unify | |
| Unilink Software Ltd | |
| Union Telecom | Oxfordshire |
| Uniphy Ltd | |
| Unipro Ltd | West Sussex |
| Unique Websites | Suffolk |
| Unique:IQ Ltd | Worcestershire |
| Unisyst Engineering plc | |
| unit36 | Greater Manchester |
| UNIT9 | |
| Unitag | Greater London |
| Unitary Ltd | |
| Unitech Computers Ltd | |
| United Agency | Lincolnshire |
| United Fintech Ltd | |
| United Kingdom Science Park Association | Essex |
| United Networks | Hertfordshire |
| United Trust Bank Ltd | |
| United Utilities Group plc | |
| Uniting Cloud | |
| Unitu | |
| Unity SEO Ltd | |
| Unity Trust Bank | |
| Universal Networks UK Ltd | Berkshire |
| Universal Quantum | East Sussex |
| Universal Smart Cards Ltd | |
| Universal Solutions 4 Business Ltd | Greater Manchester |
| Universal Technology Ltd | Hampshire |
| Universe Technology Recruitment Ltd | Greater London |
| Universitas 21 | |
| University Centre Quayside | Tyne and Wear |
| University Centre Somerset | |
| University College Birmingham | |
| University College London | Greater London |
| University College London - Department of Computer Science | Greater London |
| University College London - Department of Electronic & Electrical Engineering | Greater London |
| University College London - Department of Mathematics | Greater London |
| University College London - Gatsby Computational Neuroscience Unit | Greater London |
| University College London - Quantum Science and Technology Institute | |
| University College London Quantum Science & Technology Institute | |