| Workfox U.K. Limited | Ipswich | 1991 |
| Workocean Limited | Aberdeen | 2026 |
| World Association of Mining Lawyers | London | 2014 |
| World Carbon Mining Ltd | London | 2023 |
| World Enterprises Import & Export Limited | London | 2010 |
| World Master Petroleum Company Wmpc Ltd | London | 2021 |
| World Natural Resources Limited | Beaconsfield | 2012 |
| World OIL Group International Ltd | London | 2020 |
| World Ventures Limited | London | 2020 |
| Worldbridge Consulting Ltd | Edgware | 2024 |
| Worldwide Economic Solutions Limited | Hertfordshire | 2002 |
| Worldwide Resources USA LLC Limited | Preston | 2025 |
| Worldwide Services U.K. Ltd | Peterhead | 2013 |
| Worley Services UK Limited | Aberdeen | 2017 |
| Worth Discovery Ltd | Leeds | 2026 |
| WPH Inspections Limited | Great Yarmouth | 2012 |
| Wrekin GEO Drone Services Ltd | Market Drayton | 2015 |
| Wright N2 Services Limited | Plymouth | 2014 |
| Wright Onshore Safety Services Limited | Dereham | 2020 |
| Wright RIG Maintenance Ltd | Montrose | 2007 |
| Wrightz Ltd | Enfield | 2019 |
| WSB Group Ltd | Glasgow | 2026 |
| WTR Technical Services Limited | Cleethorpes | 2024 |
| Wwcs Intl Ltd | London | 2026 |
| WWS OIL & GAS Consultancy UK Ltd | Northampton | 2017 |
| Wwsafetyservices Limited | Liverpool | 2015 |
| Wyev Consulting Ltd | Chepstow | 2018 |
| WYN Hughes Limited | Llanelli | 2012 |
| Wynnes Group Limited | Caernarfon | 2024 |
| X Equestrius Ltd | London | 2025 |
| Xannat International Ltd | London | 2021 |
| Xeltis Ltd | London | 2025 |
| Xena Locum Limited | Manchester | 2014 |
| Xergy Group Limited | Dundee | 2018 |
| Xinyangfeng Akang (Hong Kong) Fertilizer Import and Export Limited | London | 2025 |
| Xiyue Service Limited | Cardiff | 2021 |
| Xonk Limited | Aberdeen | 2014 |
| Xplore Limited | Edmonton | 2017 |
| Xpronet Inc Limited | Stanmore | 2015 |
| Xstco Stone Ltd | Lairg | 2019 |
| XTO UK, Ltd | Fawley | 2005 |
| Xtract Duct Cleaning and Maintenance Limited | Dromore | 2023 |
| Xtract Resources PLC | London | 2004 |
| Xtreme Energy Ltd | Aberdeen | 2001 |
| Yamanaka & Co., Ltd | London | 2025 |
| YAP International Energy Group Co., Ltd | West Midlands, England | 2026 |
| Yaranc International Chemical Group (Norway) Ltd | West Midlands, England | 2025 |
| Yarrows Aggregates Limited | Beverley | 2002 |
| Yarrows Power Limited | Beverley | 2012 |
| Yeaton Energy Limited | Shrewsbury | 2018 |
| Yellow Energy Ltd | Surbiton | 2009 |
| Yenice Engineering Ltd | Cambridge | 2021 |
| Yennadon Stone Ltd | Yelverton | 2004 |
| Yield OIL Limited | Aberdeen | 2014 |
| Yiselei Haifa (International) Noble Optimization Engineering Group Co., Ltd | Cardiff | 2026 |
| Yiselie Haifa Abison Fertilizer (International) Co., Ltd | Cambridge | 2024 |
| Yiselie Hytam Chemical Co., Ltd | Cardiff | 2024 |
| Yiselie Iclchemical Group Co., Ltd | Cardiff | 2023 |
| Yiselie Lilaudo Import and Export Trading Group Co., Ltd | Cambridge | 2024 |
| Yiselie Nopron Biotechnology Co., Ltd | Cambridge | 2024 |
| York Energy (UK) Holdings Limited | London | 2019 |
| York Survey Supply Centre Limited | Clifton Moor York | 2003 |
| Yorkgravel Limited | York | 2025 |
| Yorkshire Mineral Company Limited | Carnaby | 2008 |
| Yorkshire Stones Limited | Huddersfield | 2023 |
| Yorkstone Paving Supplies Ltd | Stockport | 2021 |
| Yorkstone U.K. Limited | Cardiff | 2018 |
| Young's Pipe Fitting Ltd | Dundee | 2022 |
| Younie Marine Consultancy Ltd | Garmouth | 2012 |
| YRS Energy Limited | London | 2023 |
| YSS Rope Access Ltd | Edinburgh | 2026 |
| Yuantong Minerals Europe Ltd | London | 2025 |
| Yudin Equipment Ltd | London | 2019 |
| Yuntianhua (Qingdao) Ecological Technology Co., Ltd | London | 2025 |
| Yuntianhua International (Hong Kong) Fertilizer Import Export Limited | London | 2025 |
| Z Heating Limited | Glasgow | 2026 |
| Z-Galaxy Resources Ltd | Kington, | 2024 |
| Z2Z Trading Ltd | Manchester | 2025 |
| Zagros Energy Limited | Guildford | 2011 |
| Zambeze Mining Company Limited | Surrey | 2002 |
| Zambian Anglo Copper Limited | London | 2023 |
| Zambian Anglo Manganese Limited | London | 2021 |
| Zambian Anglo Mining Limited | London | 2020 |
| Zamin Mining Limited | Harrow | 2023 |
| Zanaga UK Services Limited | Bristol | 2011 |
| Zarmyn Limited | Huddersfield | 2019 |
| ZC Electrical Ltd | Aberdeen | 2020 |
| Zebra Energy UK Limited | Birmingham | 2023 |
| Zedcorp Ltd | London | 2020 |
| Zemarauk Limited | Leeds | 2025 |
| Zemlex Ltd. | Aboyne | 2012 |
| Zenapex Energy International Company Ltd | Basingstoke | 2022 |
| Zenith Energy Group Ltd | Aberdeen | 2024 |
| Zenith International Solutions Limited | Dundee | 2014 |
| Zenith OIL & GAS Ltd | Fowey | 2019 |
| Zenith Oilfield Technology Ltd | Aberdeen | 2003 |
| Zenocean Limited | Aberdeen | 2007 |
| Zepex GAS Ltd | Preston | 2023 |
| Zepex Petroleum Ltd | Preston | 2023 |
| Zephyr Resources (UK) Limited | Petersfield | 2016 |