| M. Hooper & Sons Limited | Blandford | 1964 |
| M. J. & D. a. Coar Limited | Chester | 2005 |
| M. J. Green Treework (Wivenhoe) Ltd | Colchester | 2005 |
| M. Keys Farms Limited | Fivemiletown | 2012 |
| M. Keys Limited | Fivemiletown | 2012 |
| M. Leggate & Sons (Produce) Limited | Boston | 1978 |
| M. O'Brien Agricultural Ltd | Bedford | 2020 |
| M. Parkin Tree Specialists Limited | London | 2010 |
| M. Poultry Services (NI) Limited | Armagh | 2011 |
| M. Rhodes (Timber Contractors & Tree Surgeons) Limited | Wetherby | 1971 |
| M. S. Ovens Limited | Bristol | 2004 |
| M. Wilkinson Limited | Chesterfield | 2006 |
| M.A. Blyth Limited | Grangemouth | 1950 |
| M.A. Fall Limited | Bedale | 2013 |
| M.A. Piper & SON Farms Ltd | Maidstone | 2026 |
| M.A. Piper & SON Ltd | Maidstone | 2026 |
| M.A. Rice & SON Limited | Haslemere | 1964 |
| M.A.C Tree Care Ltd | Sidcup | 2021 |
| M.A.D Invest Limited | Ely | 2023 |
| M.A.D Reptiles Limited | Stoke-On-Trent | 2024 |
| M.A.Hardy Limited | Barry | 1963 |
| M.A.Richards(Hawling)Limited | Cheltenham | 1964 |
| M.A.S Contracts Limited | Whitefield | 2002 |
| M.A.Tory Limited | Dorchester | 1956 |
| M.B. & J. Goodwin Limited | Hornsea | 1972 |
| M.B. Crocker Limited | Sturminster Newton | 1985 |
| M.B. Goodwin (Skipsea) Limited | Hornsea | 1976 |
| M.B.M. Farms Ltd. | Wick | 1997 |
| M.Baker Produce Limited | Boston | 1971 |
| M.C. Bristow Limited | Caterham | 1983 |
| M.C. Kisby Limited | March | 1975 |
| M.C. ROE Agricultural Services Ltd | Stowmarket | 2020 |
| M.C. Simpson (PAS) Limited | Blandford Forum | 2005 |
| M.C.Mountain and SON Limited | Sleaford | 1940 |
| M.D. Hamilton (Farms) Limited | Oxford | 1993 |
| M.D.W. Trading Limited | Norfolk | 2002 |
| M.E. Furniss & Sons (Farms) | Telford | 1969 |
| M.E. Twidale & Sons Limited | Retford | 2011 |
| M.F. Strawson (Maidenwell) Limited | Great Coates | 1990 |
| M.F. Strawson Limited | Grimsby Lincs | 1957 |
| M.F.Martin Limited | March | 1959 |
| M.G. International Limited | London | 2010 |
| M.G. Proctor Limited | Aberdeen | 2004 |
| M.Good & SON Limited | Reepham Lincoln | 1962 |
| M.H. Pryor Contracting Limited | Romford | 1993 |
| M.H.S. Farms Limited | Peterborough | 1996 |
| M.J. Bailey Limited | Waterlooville | 2011 |
| M.J. Brunton Limited | London | 1969 |
| M.J. Dawkins Limited | Barnetby | 1975 |
| M.J. Wilson Limited | North Yorkshire | 2003 |
| M.J. Worth Limited | Lincolnshire | 1970 |
| M.J.I. Farming Limited | Southampton | 1995 |
| M.J.M. Salmon Limited | Business Park, Stirling | 1985 |
| M.J.Pengelly Limited | Dorchester | 1954 |
| M.J.Read Limited | Marlborough | 1941 |
| M.J.S.Williams Limited | Salisbury, Wiltshire | 1961 |
| M.J.Tree Services Limited | Norfolk | 2004 |
| M.L.Wilson and SON Limited | Nr Alresford | 1963 |
| M.M. & J.L. Slack & Sons Limited | Belper | 2013 |
| M.M. Whidborne & Sons Limited | Winchester | 1977 |
| M.N. Lamyman Limited | Lincoln | 1987 |
| M.P. & J. Firth Limited | Huddersfield | 1999 |
| M.P. Kemp Limited | Norwich | 1979 |
| M.R. Topham Limited | Peterborough | 1998 |
| M.R. Vines & SON Limited | Chippenham | 2007 |
| M.R.L. (Seeds) Limited | Bolton | 1998 |
| M.S. Brokers Limited | Wirral | 1986 |
| M.Sadler & Sons Ltd | Pulborough | 2026 |
| M.Schneider Electrical Ltd | Nairn | 2025 |
| M.T. Aves and Sons Limited | Diss | 2006 |
| M.V Deeside BCK595 Ltd | Peterhead | 2018 |
| M.V. Caspian | Banffshire | 2003 |
| M.V. Quantus Limited | Aberdeen | 1994 |
| M.V. Resolute Limited | Buckie | 2003 |
| M.W. Herdman Forestry Solutions Limited | Northumberland | 2008 |
| M.W. Nash Farming Limited | Taunton | 2018 |
| M.W.H. & H. Ward Estates Limited | Cardiff | 1990 |
| M.W.Smith Shellfish Limited | King'S Lynn | 2000 |
| M1 Services Limited | Melton Mowbray | 2017 |
| M2 Square Entertainment Ltd | London | 2026 |
| M2F Agri Limited | Enniskillen | 2024 |
| M3 Harvesting Ltd | Llandovery | 2022 |
| MA & EJ Bennett Limited | Devon | 2007 |
| MA & MRS JA Griffiths Limited | Llandrindod Wells | 2009 |
| MA BMS Electrical Ltd | Rainham | 2017 |
| MA Veggies Ltd | Northampton | 2024 |
| MA Zhicheng Ltd | Manchester | 2024 |
| Maacal Limited | Taunton | 2002 |
| MAB Farming Limited | Southminster | 2021 |
| MAB Flowers Limited | Spalding | 2018 |
| Mablekin Limited | Watford | 2025 |
| Mably Dairies Limited | Wadebridge | 2020 |
| Mably Farms Limited | Cornwall | 1961 |
| MAC Dive Ltd | Tarbert | 2024 |
| MAC Equestrian Melrose Ltd | Melrose | 2026 |
| MAC Farms Ltd | Omagh | 2010 |
| MAC Tree Services Ltd | Belper | 2013 |
| MAC Tree Surgery and Fencing Limited | Lowestoft | 2024 |
| MAC24 Limited | Wigston | 2024 |
| Macara Gundogs Limited | Manchester | 2023 |