| Hy-Standard Ltd | Barry | 2013 |
| Hy-Tek Solutions Limited | Bishop'S Stortford | 2024 |
| Hy-Tools Limited | Strood | 2007 |
| HYA Football Limited | Borehamwood | 2019 |
| Hyacinth Modelling Ltd | Nottingham | 2023 |
| Hyalpharm Limited | Chester | 2015 |
| Hyams & Partridge Electrical Contractors Ltd | Chard | 2013 |
| Hybrid and Virtual Events Ltd | Newton Abbot | 2018 |
| Hybrid Fencing Limited | Chelmsford | 2014 |
| Hybrid Machine Intelligence Ltd | Sandown | 2025 |
| Hybrid Powergen Limited | Waltham Abbey | 2016 |
| Hybrid Training and Consulting Limited | Hornchurch | 2013 |
| HYBRID3D Ltd | London | 2013 |
| Hycare Holdings Limited | Feltham | 1976 |
| Hycolin Limited | Coventry | 2020 |
| Hydal Limited | London | 2017 |
| Hyde Aerial Satellites Ltd | Basildon | 2013 |
| Hyde AV Solutions Ltd | Basildon | 2013 |
| Hyde Developments UK Limited | Barnsley | 2003 |
| Hyde Park Corner Ltd | Glossop | 2019 |
| Hyde Park Holdings Nominee 1 Ltd | London | 2025 |
| Hyde Park Holdings Nominee 2 Ltd | London | 2025 |
| Hyde Park Holdings Nominee 3 Ltd | London | 2025 |
| Hyde Park London Limited | London | 2020 |
| Hyde Road Tyres Limited | Manchester | 2000 |
| Hyde-Crete Limited | Coventry | 1936 |
| Hyderabad House Limited | Brentford | 2021 |
| Hydra (South West) Limited | St. Columb | 1992 |
| Hydra Construction Ltd | Royal Wootton Bassett | 2025 |
| Hydra Drones Ltd | Royal Wootton Bassett | 2025 |
| Hydra Gleam Limited | London | 2009 |
| Hydra-Pak Limited | Euxton Lane, Euxton | 2021 |
| Hydracy UK Ltd | London | 2025 |
| Hydrafit (Properties) Limited | Wolverhampton | 2008 |
| Hydrafit Limited | Wolverhampton | 2019 |
| Hydramatix Limited | Tunbridge Wells | 1999 |
| Hydramist Limited | Attleborough | 2011 |
| Hydrangea RTM Company Limited | Bushey | 2026 |
| Hydraparts Ltd | Gloucester | 2026 |
| Hydraroll Limited | Liverpool | 2002 |
| Hydraseeders (Southern) Limited | Derby | 1969 |
| Hydrastar Limited | Ely | 2011 |
| Hydratrak Ltd | Billingham | 2024 |
| Hydraulic Control Limited | Reading | 2005 |
| Hydraulic Manifolds UK Ltd | Bedlington | 2012 |
| Hydraulics (Ireland) Limited | Dungannon | 1970 |
| Hydraulics UK Ltd | Ashbourne | 1998 |
| Hydravalve UK Limited | Wilmslow | 2017 |
| Hydro Fitness Solutions Limited | Stoke-On-Trent | 2009 |
| Hydro GB Limited | Rochdale | 2009 |
| Hydro Panel Limited | 3 Dorset Rise | 2015 |
| Hydro Physio Limited | Broseley | 2005 |
| Hydro Waves Ltd | London | 2025 |
| Hydro-Flo Ltd | Crediton | 2012 |
| Hydro-Head Industry Group Ltd | London | 2017 |
| Hydroblast Group Limited | Northallerton | 2019 |
| Hydroblast Technologies Ltd | Northallerton | 2019 |
| Hydroblast UK Rentals Limited | Northallerton | 2019 |
| Hydroblasting Rentals Ltd | Northallerton | 2019 |
| Hydroblasting Training Ltd | Northallerton | 2019 |
| Hydrocarbon Economics Limited | London | 2015 |
| Hydrocarbon Services GB Ltd | Bradford | 2020 |
| Hydrocarbon Ventures Limited | Bath | 2024 |
| Hydrocells Ltd | Braintree | 2020 |
| Hydrocquel Ltd | Bedford | 2011 |
| Hydrofleet Ltd | London | 2025 |
| Hydroflex-Eu Limited | Hook | 2016 |
| Hydroflow Limited | Teignmouth | 2014 |
| Hydrogen Capital Growth (Nominee) Limited | London | 2021 |
| Hydrogen Coffee Limited | Hatfield | 2023 |
| Hydrogen Energy Solutions UK Ltd | Wakefield | 2025 |
| Hydrogen Services Limited | Hatfield | 2023 |
| Hydrogen Supplies Limited | Woking | 1993 |
| Hydrohertz Thermal Solutions Limited | Nottingham | 2023 |
| Hydroinformatics Solutions Ltd | Birmingham | 2020 |
| Hydrolectrix IP Limited | Liverpool | 2022 |
| Hydrolectrix Ltd | Liverpool | 2014 |
| Hydrolink Ltd | London | 2015 |
| Hydromotion Limited | Sheffield | 2021 |
| Hydromountan Engineering Ltd | London | 2023 |
| Hydroplan Group Limited | Wimborne | 2021 |
| Hydroplan Properties Limited | Wimborne | 2013 |
| Hydroprocessing Associates Europe Ltd | Scunthorpe | 2009 |
| Hydroproof Limited | Bamber Bridge | 1980 |
| Hydrorelax Ltd. | Beckenham | 2016 |
| Hydrorider Limited | Stoke-On-Trent | 2009 |
| Hydrorider UK Limited | Stoke-On-Trent | 2009 |
| Hydroseal Canada Piping Systems Co., Limited | London | 2017 |
| Hydrosolve Limited | Pudsey | 2023 |
| Hydrosphere Navaids Limited | Alton | 2012 |
| Hydrospin Limited | Stoke-On-Trent | 2013 |
| Hydrosub (Asia) Limited | Lowestoft | 2010 |
| Hydrosun Limited | Hamilton | 2017 |
| Hydrosure Holdings Limited | Telford | 2021 |
| Hydrotech Maintenance Ltd | Bradford | 2019 |
| Hydrov Ltd | Barnsley | 2022 |
| Hydrus (UK) Limited | Manchester | 2014 |
| Hydrus Group Limited | Loughborough | 2009 |
| Hyek Cleaning Service Ltd | Bradford | 2025 |
| Hyfield Management Services Limited | Grange Over Sands | 1995 |