| Ainsworth & Wells Ltd | Chesham | 2012 |
| Ainsworth Accountants Limited | Preston | 2005 |
| Ainsworth Aviation Consultancy Ltd | Eastbourne | 2018 |
| Ainsworth Consultancy Ltd | Congleton | 2023 |
| Ainsworth Consultancy Services Ltd | London | 2020 |
| Ainsworth Consulting Group Ltd | York | 2003 |
| Ainsworth Freehold Limited | Manchester | 2013 |
| Ainsworth Surveying Services Limited | Manchester | 1997 |
| Ainsworths Financial Services Limited | Nelson | 2000 |
| Ainsworths Limited | Lancashire | 2004 |
| Aintree Automobile Racing Company Limited | Liverpool | 2020 |
| Aintree Enterprises Limited | Liverpool | 2016 |
| Aintree House Consulting Limited | Wolverhampton | 2018 |
| Aintree Plastics (Holdings) Limited | Altrincham | 2016 |
| Aintu Ltd | Watford | 2019 |
| Ainu.Collective Ltd | London | 2024 |
| Ainzoalf Engineering Ltd | Widnes | 2026 |
| AIO Consulting Limited | Banbury | 2016 |
| AIO Engineering Services Ltd | Warrington | 2022 |
| AIO Labs Limited | London | 2026 |
| AIO Partners Ltd | Leeds | 2013 |
| AIO Services Ltd | London | 2016 |
| AIO VET Limited | Leeds | 2023 |
| Aioi R&D LAB Limited | London | 2022 |
| Aiolos BIO Limited | London | 2023 |
| Aiolos Engineering Limited | London | 2024 |
| Aiolos Renewables Limited | Bristol | 2026 |
| Aion Accounting Technologies Ltd | York | 2024 |
| Aion Advisory Ltd | Edgware | 2024 |
| Aion Advocacy Ltd | London | 2025 |
| Aion Altair Ltd | London | 2025 |
| Aion CFO Services Ltd | Hemel Hempstead | 2026 |
| Aion Consultancy Ltd | London | 2019 |
| Aion Corporate Finance Limited | Brighton | 2009 |
| Aion Energy Ltd | London | 2026 |
| Aion Gaming Ltd | Brighton | 2025 |
| Aion Platform Ltd | London | 2023 |
| Aion Process Engineering Ltd | Redcar | 2018 |
| Aion Project Engineering Ltd | London | 2025 |
| Aion Projects Ltd | Birchington | 2018 |
| Aion Property Certificates Ltd | Enfield | 2023 |
| Aion Renewable Energy Consultants Ltd | Hounslow | 2025 |
| Aion Silicon Holdings Limited | London | 2010 |
| Aion Silicon Limited | London | 2002 |
| Aionis Ventures Limited | Bolton | 2026 |
| Aionova Holdings Ltd | London | 2023 |
| Aios Group Limited | London | 2015 |
| Aiotechnics Ltd | High Bickington | 2021 |
| AIP Amarya Limited | Droitwich | 2011 |
| AIP Architects Limited | Walsall | 2013 |
| AIP Design Ltd. | Croydon | 2012 |
| AIP Management Ltd | Loughton | 2019 |
| AIP Studio Ltd | London | 2025 |
| AIP1ZERO Limited | London | 2023 |
| Aipa Ltd | Aberdeen | 2025 |
| Aiparenting Ltd | London | 2026 |
| Aipf (UK) Limited | Eastleigh | 2012 |
| Aiphion Ltd | Derby | 2016 |
| Aiphos Engineering Limited | Cardiff | 2015 |
| Aiphos Limited | Abergavenny | 2026 |
| Aipicom Limited | Enfield | 2006 |
| Aipix Ltd | Mildenhall | 2023 |
| Aiplify Caelestis Research Ltd | London | 2025 |
| Aiplify Research Ltd | London | 2024 |
| Aipolas Limited | Cambridge | 2012 |
| Aippi United Kingdom | London | 1927 |
| Aipros Design Ltd | London | 2016 |
| Aipu Shide IP Limited | London | 2024 |
| AIQ Consultancy Ltd | Wimborne | 2023 |
| AIQ Consulting Limited | Wallingford | 2013 |
| AIQ Training Ltd | London | 2021 |
| Aiqo Limited | Nairn | 2015 |
| Aiqtec Ltd | St. Andrews | 2014 |
| Air & Ventilation Testing UK Ltd | Burnley | 2025 |
| Air 23 Limited | Chester | 2016 |
| Air 66 Design Limited | Nottingham | 2018 |
| Air 88 Ltd | London | 2025 |
| Air Accountancy Ltd | Edinburgh | 2026 |
| Air Accountancy Services Ltd | Swaffham | 2025 |
| Air Accounting Limited | Whitchurch | 2016 |
| Air ADZ Limited | Ilfracombe | 2026 |
| Air Alliance Ltd | Cannock | 2009 |
| Air Analytics Ltd | Derby | 2019 |
| Air and Acoustic Consultants (Birmingham) Limited | Birmingham | 2024 |
| Air and Acoustic Consultants (London) Limited | Birmingham | 2024 |
| Air and Acoustic Consultants Limited | Birmingham | 2018 |
| Air and Ground Aviation Holdings Limited | Shirleywich | 2016 |
| Air and Isla Ltd | Bolton | 2025 |
| Air and Space Evidence Ltd | Devizes | 2014 |
| Air and Space Power Consulting Ltd | Sleaford | 2019 |
| Air BAG Stopper Holdings Limited | Edinburgh | 2007 |
| Air Business Advisors Limited | Richmond | 1999 |
| Air Capture Consulting Limited | Wimborne | 2023 |
| Air Cargo Support Ltd | London | 2025 |
| Air Cargo Transport Limited | Coleorton | 2006 |
| Air Charter Service Trustee Company Ltd. | Surbiton | 2007 |
| Air Charter Travel Holdings Limited | Gatwick | 2019 |
| Air Classics Ltd | Ballindalloch | 2021 |
| Air Combat Evolution Limited | London | 2021 |
| Air Compression Technology Limited | Sheffield | 2003 |