| Aleksa Studio Ltd | Cockfosters | 2014 |
| Aleksandra Filipovic Ltd | Bromley | 2015 |
| Aleksandra Himiceva Ltd | London | 2024 |
| Aleksandra King Limited | Chesham | 2014 |
| Aleksandra Kingo Ltd | London | 2015 |
| Aleksandra Kowalik Ltd | London | 2019 |
| Aleksandria Sciences Limited | Chesterfield | 2011 |
| Alekseevaph Ltd | London | 2025 |
| Aleksi Tammi Limited | London | 2018 |
| Alekx Ltd | London | 2026 |
| Alel Sheq Solutions Ltd | Suffolk | 2023 |
| Alelto Ltd | London | 2024 |
| Alem Consultancy Limited | Grays | 2020 |
| Alemana Limited | Inverness | 2014 |
| Alemania Limited | Hertford | 2018 |
| Alemar Limited | Palmers Green | 2011 |
| Alemara Engineering Limited | London | 2015 |
| Alemara Resi Ltd | London | 2025 |
| Alemare Solutions Limited | Milton Keynes | 2006 |
| Alembia Intellectual Property Limited | Macclesfield | 2017 |
| Alembic Products Limited | Liverpool | 1980 |
| Alembic Research Limited | Glasgow | 2005 |
| Alembic Strategy Limited | London | 2016 |
| Alemira UK Ltd | Egham | 2021 |
| Alemis Board Solutions Limited | Hemel Hempstead | 2024 |
| Alemo Ltd | Liphook | 2018 |
| Alemso Limited | Harpenden | 2020 |
| Alemus Limited | Maidenhead | 2013 |
| Alen Norway Consulting and Service Limited | Manchester | 2026 |
| Alena Ltd | Liverpool | 2014 |
| Alena Todorov Limited | London | 2020 |
| Alencer Consultancy Ltd | London | 2017 |
| Alencia Designs Limited | Harlow | 2020 |
| Alenco (Holdings) Limited | Hemel Hempstead | 1950 |
| Alendale Associates Ltd | West Malling | 2019 |
| Alendi Consulting Limited | Alresford | 2014 |
| Alendos Consulting Limited | Enfield | 2026 |
| Alenia Consulting UK Limited | London | 2019 |
| Alenik Group Ltd | Greenford | 2026 |
| Alensi Studios Ltd | Arlesey | 2025 |
| Alent Finance Limited | Woking | 2012 |
| Alent Holdings Brazil Limited | Woking | 2003 |
| Alent Investments Limited | Woking | 2012 |
| Alent Limited | Woking | 2012 |
| Alent New Finance (UK) Limited | Woking | 2012 |
| Alent New Mexico Holdings Limited | Woking | 2012 |
| Alentis Recruitment Ltd | Sutton | 2020 |
| Alento Ltd | Huntingdon | 2017 |
| Aleon Limited | Beverley | 2013 |
| Aleph Energy Ltd | London | 2020 |
| Aleph Insights Limited | Hoddesdon | 2014 |
| Aleph One Limited | Cambridge | 1971 |
| Aleph Saltfleetby Ltd | London | 2021 |
| Aleph Stratagems Limited | Wadhurst | 2021 |
| Aleph Strategies Limited | London | 2018 |
| Aleph Studio London Limited | Edgware | 2018 |
| Aleph Studio Ltd | Leeds | 2020 |
| Aleph TAV Limited | London | 2012 |
| Alepharium Limited | London | 2025 |
| Alephbetshin Ltd | Brighton | 2026 |
| Alephoo Group Ltd | Egham | 2020 |
| Aleppian Advisory Ltd | London | 2025 |
| Alepuz Legal Consulting Limited | Bromley | 2012 |
| Aleqtra Limited | Weston-Super-Mare | 2025 |
| Alera Accounting & Advisory Limited | Cardiff | 2025 |
| Alera Advisory Ltd | London | 2026 |
| Alercell (UK) Ltd | London | 2023 |
| Alere AS Holdings Limited | Berkshire | 2011 |
| Alere UK Holdings Limited | Berkshire | 2001 |
| Alerion Consulting Group Ltd | Taunton | 2019 |
| Alermay Flat Management Limited | East Sussex | 1993 |
| Aleron Group Limited | Farnham | 2009 |
| Aleron Partners Limited | Farnham | 2011 |
| Aleroshoots Ltd | London | 2024 |
| Alert 24 Hour Plumbing Ltd. | Glasgow | 2008 |
| Alert CMS Limited | Driffield | 2013 |
| Alert Inspection Services Ltd | Warrington | 2018 |
| Alert NOT Alarmed Enterprises Limited | Edinburgh | 2018 |
| Alert One Ltd | Warwickshire | 2007 |
| Alert PPM Limited | Nottingham | 2011 |
| Alert Response Recruitment Ltd | London | 2025 |
| Alert Training Ltd | Lancaster | 2004 |
| Alert Training UK Limited | Salisbury | 2007 |
| ALERT15 Ltd | Billingshurst | 2002 |
| Alertcom Limited | Epsom | 2020 |
| Ales Consulting Ltd | Norwich | 2024 |
| Alesandre Management Ltd | London | 2016 |
| Alesbury FM Solutions Ltd | Ruislip, | 2026 |
| Alesco Services Ltd | Exeter, Ex2 8He | 2016 |
| Aleshh Limited | Seven Oaks | 2025 |
| Alesi Marketing Ltd | Chatham | 2026 |
| Alesi Surgical Limited | Cardiff | 2007 |
| Alesia Media Ltd | Bury St. Edmunds | 2025 |
| Alessandra Bosi Design Ltd | London | 2026 |
| Alessandra Fineschi Consultant Ltd | London | 2015 |
| Alessandra Studio Ltd | London | 2005 |
| Alessandri Design Ltd | London | 2014 |
| Alessandro Canova Design Limited | London | 2017 |
| Alessandro Caruso Architecture and Interiors Limited | Beverley | 2014 |
| Alessandro Clima Ltd | London | 2005 |