| Apatura Project 24 Ltd | Altrincham | 2024 |
| Apatura Project 25 Ltd | Altrincham | 2024 |
| Apatura Project 26 Ltd | Altrincham | 2024 |
| Apatura Project 27 Ltd | Altrincham | 2024 |
| Apatura Project 28 Ltd | Altrincham | 2024 |
| Apatura Project 29 Ltd | Altrincham | 2024 |
| Apatura Project 30 Ltd | Altrincham | 2024 |
| Apatura Project 31 Ltd | Altrincham | 2024 |
| Apatura Project 32 Ltd | Altrincham | 2024 |
| Apatura Project 33 Ltd | Altrincham | 2024 |
| Apatura Project 34 Ltd | Altrincham | 2024 |
| Apatura Project 35 Ltd | Altrincham | 2024 |
| Apatura Project Holding 3 Ltd | Altrincham | 2023 |
| Apatura Project Holding 4 Ltd | Altrincham | 2023 |
| Apatura Project Holding 5 Ltd | Altrincham | 2024 |
| Apatura Solar Ltd | Altrincham | 2014 |
| Apegg Solutions Limited | Llandudno | 2017 |
| Apex Air Conditioning Limited | Weston Super Mare | 1994 |
| Apex Capital Holdings Ltd | Greenhithe | 2021 |
| Apex Energy Ltd | King'S Lynn | 2015 |
| Apex Renewables North East Limited | Newcastle Upon Tyne | 2024 |
| Apex Telecoms & Energy Limited | Cardiff | 2020 |
| Apex Urban Limited | Edinburgh | 2024 |
| Apex Utilities Ltd | Barnet | 2022 |
| Apex Volt Solutions Ltd | Llanharan | 2025 |
| Apexfield General Trading Limited | Glasgow | 2026 |
| Apexity Developments Ltd | London | 2025 |
| APH Electrical Limited | Westerham | 2015 |
| APL Utilities Limited | Brandon | 2024 |
| Apollo Air Conditioning Ltd | Scunthorpe | 2013 |
| Apollo Commissioning Services Ltd | Guildford | 2018 |
| Apollo Energy (UK) PVT Ltd | Edgware | 2025 |
| Apollo Energy Group Ltd | Dunstable | 2025 |
| Apollo Power Ltd | London | 2023 |
| Apollo Solar Ltd | Enniskillen | 2025 |
| Apollomech Services Limited | Maidstone | 2022 |
| Appin Hydro Limited | Lochgilphead | 2015 |
| Appin Wind Farm Limited | London | 2020 |
| Apple Technical Solutions Limited | Bridgwater | 2003 |
| Appledore Shipbuilders Limited | Dorset | 1922 |
| Applegreen Electric UK Limited | Newport Pagnell | 2021 |
| Applegreen Electric UK Service Areas Limited | Newport Pagnell | 2022 |
| Applied Electric Services Midland Limited | Lichfield | 2015 |
| Applied Solar Ltd | London | 2010 |
| APR Energy Holdings Limited | London | 2009 |
| Apricate Energy Ltd | Shrewsbury | 2017 |
| Apropos Energy Limited | Bristol | 1999 |
| APS Energy Ventures Limited | Torquay | 2025 |
| APS GAS Services Limited | Wolverhampton | 2025 |
| Apus Energy Limited | Cardiff | 2014 |
| AQ Energy Ltd | Nottingham | 2025 |
| Aqgas UGV Limited | Nottingham | 2023 |
| Aqua Ignis Limited | High Wycombe | 2012 |
| Aqua Mechanical Services Ltd | Maidstone | 2017 |
| Aquatech Installations Ltd | Birmingham | 2026 |
| Aquatherm Energy Ltd | Morpeth | 2025 |
| Aquind Limited | London | 2008 |
| AR Cooling (NE) Limited | South Shields | 2019 |
| AR Electrical South Ltd | Swindon | 2024 |
| AR Jones Electrical Limited | Pwllheli | 2013 |
| AR Plumbing Heating Construction Company Ltd | Bury | 2019 |
| AR006 GF Solar Limited | Bristol | 2021 |
| AR108 Bolt Solar Farm Limited | Bristol | 2021 |
| Arab European Investment Corp. Limited | Sittingbourne | 2017 |
| Arabelle Marine UK Limited | Rugby | 2013 |
| Aragorn Solar Farm Limited | Stockport | 2022 |
| Aran Hydro CYF | Bala | 2015 |
| ARB (Bellshill) Limited | Dungannon | 2020 |
| Arbroath Energy Storage Park Limited | London | 2024 |
| Arbroath Limited | London | 2019 |
| Arbroath NET Zero Ltd | Edinburgh | 2023 |
| Arbuthnott Turbines Limited | Fareham | 2014 |
| ARC Electrics Ltd | Rickmansworth | 2023 |
| ARC Power Ltd | Reigate | 2014 |
| ARC Right Electrical Limited | Brixham | 2012 |
| ARC Solar Limited | Bideford | 2021 |
| Arca Holding Associated Engineers Ltd | London | 2017 |
| Arccap Holdings Limited | London | 2024 |
| Arcform AM Limited | London | 2026 |
| Arcform Networks Ltd | London | 2026 |
| Archair Limited | Swindon | 2022 |
| Archers Air Conditioning and Ventilation Ltd | London | 2025 |
| Archway Bess SPV Limited | Kidlington | 2023 |
| Arco Building Services Limited | Rugeley | 2013 |
| Arco Kiniun Limited | Sheffield | 2021 |
| Arco Services Limited | Willenhall | 1998 |
| Arctic Blast Ltd | Ilford | 2025 |
| Arctic Cooling Services Limited | Weybridge | 2016 |
| Arctic Flame Limited | Bracknell | 2024 |
| Arctic Refrigeration Services (NI) Ltd | Co Armagh | 2005 |
| Arcturus Solar Limited | London | 2017 |
| Arda Electrical Ltd | Mitcham | 2014 |
| Ardboe Agri Energy Ltd | Cookstown | 2012 |
| Ardchattan Hydro Limited | Perthshire | 2005 |
| Ardenham UK Limited | London | 2025 |
| Ardenix Developments Ltd | London | 2025 |
| Ardenix Holdings Ltd | Maidenhead | 2026 |
| Ardent Energy Trading Limited | London | 2019 |
| Ardhu Power Limited | Isle Of Mull | 2012 |
| Ardleigh Solar Limited | Faversham | 2013 |