| Aberdeen Consultancy Ltd | Dundee | 2008 |
| Aberdeen Drilling Management Limited | Aberdeen | 1999 |
| Aberdeen Minerals Exploration Ltd | Ellon | 2018 |
| Aberdeen Minerals Ltd | London | 2020 |
| Aberdeen Oilfield Services Ltd | Aberdeen | 2015 |
| Aberdeen Petroleum Engineering Consultants Limited | Peterculter | 1991 |
| Aberdeen Roughnecks Limited | Westhill | 2009 |
| Abhita Land Solution Ltd | Cardiff | 2025 |
| Able Oiltools Ltd | London | 2025 |
| Abraham Elite Ltd | Covent Garden | 2023 |
| Absafe Access Limited | Stranraer | 2015 |
| Absafe Ltd | Motherwell | 2014 |
| Absailing NDT Ltd | Lincolnshire | 2025 |
| Absis Limited | Redhill | 2007 |
| Abslide Ltd. | Edinburgh | 2001 |
| Absolute Stone Ltd | London | 2018 |
| ABX Enterprises Ltd | Hereford | 2026 |
| Abyss Engineering Limited | Tooting | 2007 |
| Abyssinian Gold PLC | London | 2020 |
| ABZ Contracting Ltd | Stonehaven | 2022 |
| Abzinfo Limited | Montrose | 2005 |
| AC Kelly Ltd | Kirkcudbright | 2025 |
| AC OIL Consulting Ltd | Tranent | 2016 |
| Acasta Energy Services Limited | Tavistock | 2014 |
| Accentrica Energy Ltd | London | 2025 |
| Access Ecosse Limited | Plymouth | 2017 |
| Access GAS Limited | Rotherham | 2020 |
| Access NDT Limited | Aberdeen | 2009 |
| Access Offshore Ltd | Glasgow | 2023 |
| Access Rigging Limited | Sunderland | 2026 |
| Access Shore Limited | St. Helens | 2025 |
| Access Solutions (GT Yarmouth) Limited | Great Yarmouth | 2015 |
| Access Solutions Scotland Ltd | Aberdeen | 2022 |
| Access Tech Ltd | Truro | 2011 |
| ACCESS2ENERGY Ltd | Buckie | 2017 |
| Accokg PLC | Maidenhead | 2024 |
| Accsensum Ltd | London | 2019 |
| Accuenergy Solutions Ltd | Aberdeen | 2019 |
| Accumin Solutions Ltd | Magherafelt | 2017 |
| Acdd Ltd | Mitcham | 2007 |
| Ace Aggregate Processing Limited | Bristol | 2014 |
| Ace Global Logistics Ltd | London | 2012 |
| Ace Petrochem Ltd | Glasgow | 2010 |
| Ace Subsea Inspection Services Ltd | Skipton | 2022 |
| Aceblade Limited | Brighouse | 1985 |
| Acer Petroleum Xploration Ltd | Wirral | 2026 |
| Achaean Petroleum Consulting Limited | Cirencester | 1996 |
| ACI Oilfield Services Limited | Isleworth | 2026 |
| Acla Holdings Limited | London | 2017 |
| ACM82 Logistics Ltd | Westhill | 2016 |
| Acquiesce Technical Solutions Limited | Sale | 2015 |
| Acquire Offshore Marine Services Ltd | Bournemouth | 2020 |
| Acresford Sand and Gravel Limited | | 1963 |
| Acronym Limited | Shefford | 2001 |
| ACS Hydrocarbons Limited | Reading | 2014 |
| ACT Completions Ltd | Montrose | 2022 |
| Acth Limited | London | 2014 |
| Active Minerals International Ltd. | London | 2025 |
| Actual Aggregates Limited | Hereford | 2021 |
| AD Energy Europe Ltd | Leigh-On-Sea | 2017 |
| ADA OIL and GAS Services Ltd | Orpington | 2022 |
| Adam Chase Commodities Ltd | London | 2025 |
| Adam Wheeler Mining Consultant Ltd | Cornwall | 2018 |
| Adamo Energy (UK) Limited | Bridgend | 2007 |
| Adatho Engineering Limited | Aberdeen | 2024 |
| Adderson Aggregates Ltd | Greenhithe | 2019 |
| Addison Mining Services Ltd | Waltham Abbey | 2014 |
| Addison Mining Ventures Ltd | London | 2026 |
| Adedejico Limited | Oxford | 2022 |
| Adeelan Ltd | Cookstown | 2025 |
| Adeptomines Limited | Newport | 2018 |
| ADG Oilfield Services Limited | Great Yarmouth | 2014 |
| Adghal Oilfield Supplies Ltd | London | 2025 |
| Adgl Limited | Whitby | 2013 |
| Adilifting Ltd | Wallsend | 2019 |
| Adit Development UK Ltd | Cambridge | 2022 |
| ADM Energy PLC | London | 2004 |
| Admc Consultants Limited | Glasgow | 2015 |
| Adonai Proactive Service Limited | Colchester | 2018 |
| Adpq Limited | Hemel Hempstead | 2023 |
| Adriatik Stone Ltd | London | 2026 |
| ADS Consult Services Ltd | Gillingham | 2025 |
| Adura Energy Limited | London | 2010 |
| Advance Energy TL Limited | Stockbridge | 2020 |
| Advance Quarries Ltd | Bellshill | 2011 |
| Advanced Earth Metals Ltd | Milton Keynes | 2020 |
| Advanced Future Solutions Ltd | Harlow | 2024 |
| Advanced Innergy Contracting Ltd | Gloucester | 2008 |
| Advanced Material Processing Limited | Stirling | 2015 |
| ADY 1 Limited | Whitby | 2011 |
| AE Geosciences Limited | Shepperton | 2019 |
| AE River Management Ltd | Dunfries | 2012 |
| Aedes Energia Limited | Woking | 2024 |
| Aemek Solutions Limited | Barking | 2021 |
| AER INT. Ltd | Inverurie | 2022 |
| AER Minerals Ltd | Thatcham | 2026 |
| Aerial Inspection & Mapping Surveys Ltd. | Chesterfield | 2015 |
| Aetechservices Limited | Aberdeen | 2013 |
| Aethel Mining Europe Limited | London | 2019 |
| Afdrill Ltd | London | 2020 |