| Lucky Drinks 4 U LtdSunderland, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2007 |
| Lunzer Wine Group LimitedRichmond, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2015 |
| Luxpak LimitedPeterborough, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2015 |
| Lw Theatres Group LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2000 |
| Macdonald & Muir LimitedEdinburgh, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1936 |
| Mace LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1989 |
| Madeira London LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2015 |
| Mail Boxes Etc LtdWarwick, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1995 |
| Malcouk LtdWinchester, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2006 |
| Mallams LtdKidlington, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1997 |
| Manor Park Drinks LtdChislehurst, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2014 |
| Maramia LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2007 |
| Maree Wine LtdWellingborough, United Kingdom · UKmareewine.com · checked 28 Oct 2026 | UK | 1 | – | – | – | – | 2025 |
| Margetts Fund Management LimitedBirmingham, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2001 |
| Margiotta LimitedNewbridge, United Kingdom · UKmargiotta.co.uk · checked 28 Oct 2026 | UK | 1 | – | – | – | – | 1979 |
| Mark Thompson Lifesciences LtdBishop Auckland, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2015 |
| Marlin Equity Partners LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2012 |
| Marriott Webb LtdCardiff, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2023 |
| Maschio Gaspardo UK LimitedLincoln, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2018 |
| Mathies Trading LtdBrockenhurst, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| Matthew Jukes Productions LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1998 |
| Mavega UK LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2013 |
| Mccann Manchester LimitedMacclesfield Cheshire, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1986 |
| Mccloskey International LtdBirmingham, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1988 |
| Mclaren Racing LimitedWoking, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1980 |
| Mcmillan Motorsport LimitedBurton on Trent, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2012 |
| Mcqueens Flowers LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| Mde Services Group LimitedBracknell, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2016 |
| Me Group International PLCEpsom, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1962 |
| Meadow Foods LtdChester, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1992 |
| Mechanised Project ManagementLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1946 |
| Mecm, LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1996 |
| Medagio LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2016 |
| Metmix LimitedUnited Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1990 |
| Mi Doudou LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2019 |
| Microsoft LimitedReading, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1982 |
| Mid Atlantic Productions LtdPyrford, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1987 |
| Milestone LtdUnited Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2003 |
| Millbank Financial Services LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1986 |
| Mills & Reeve LLPLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2007 |
| Mindshare Media UK LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1997 |
| Mission Bay LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2011 |
| Mitchell Potatoes LtdRugby, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1980 |
| Model Farm Shop Ltd.Bradford, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2012 |
| Modern Contradiction LimitedShrewsbury, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| Moke Fine Wines LtdCirencester, United Kingdom · UKmokefinewines.co.uk · checked 28 Oct 2026 | UK | 1 | – | – | – | – | 2010 |
| Moncharm LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2007 |
| Mondrian LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1998 |
| Monex Europe LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2006 |
| Montealegre Company LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2015 |