| Medical Device Interoperability Ltd | Professional & scientific | 2024 |
| Medical Information Technology International Limited | Information & communication | 2016 |
| Medical Research Network Limited | Professional & scientific | 2006 |
| Medical Workforce Limited | Administrative & support | 2018 |
| Medical-Locums Ahp/Hss Ltd | Administrative & support | 2017 |
| Medical-Locums Doctors Ltd | Administrative & support | 2017 |
| Medical-Locums Group Ltd | Health & social care | 2015 |
| Medical-Locums Nursing Ltd | Health & social care | 2017 |
| Medicallab Limited | Information & communication | 2006 |
| Medicare Direct Limited | Health & social care | 2018 |
| Medicare Marketing Ltd | Professional & scientific | 2026 |
| Medicare Support & Housing Ltd | Public administration | 2021 |
| Medici Investments Limited | Real estate | 2023 |
| MEDICI2 Investments Ltd | Real estate | 2023 |
| Medifinance Limited | Financial services | 2003 |
| Medimunus Ltd | Wholesale & retail | 2025 |
| Medina House Ltd | Information & communication | 2013 |
| Medipharmaco Law Ltd | Information & communication | 2025 |
| Medise Limited | Health & social care | 2022 |
| Mediterranean Leisure Group Limited | Hospitality | 1983 |
| Mediva Pharma Limited | Wholesale & retail | 2011 |
| Medix Professionals Ltd | Health & social care | 2022 |
| Medlow Estates Limited | | 1946 |
| Medocal Pharma Distributors Ltd | Wholesale & retail | 2020 |
| Medpath Global Ltd | Information & communication | 2025 |
| Medpower Group Ltd | Professional & scientific | 2025 |
| Medra Health Ltd | Wholesale & retail | 2025 |
| Medraus Services Limited | Wholesale & retail | 2024 |
| Medskin Aesthetics Ltd | Other services | 2025 |
| Medtec Ltd | Health & social care | 2019 |
| Medtech Makers LAB Limited | Professional & scientific | 2017 |
| Medtrust Care Ltd | Health & social care | 2025 |
| Medxcel Ltd | Education | 2025 |
| Meeg Training and Employment Services Ltd | Information & communication | 2023 |
| Meem Group Limited | Information & communication | 2023 |
| Meenaban Limited | Information & communication | 2017 |
| Meens Wageman Limited | Professional & scientific | 2014 |
| Meexy MC Ltd | Construction | 2014 |
| Mega Bricks Ltd | Real estate | 2025 |
| MEGA4 Ltd | Wholesale & retail | 2020 |
| Megaco Limited | Wholesale & retail | 2018 |
| Megamerchantdeals Ltd | Wholesale & retail | 2024 |
| Megapower for Energy Solutions and Contracting Limited | Energy | 2017 |
| Mehdi Inc Ltd | Construction | 2018 |
| Mehgof Limited | Professional & scientific | 2015 |
| Mehmipharm Ltd | Health & social care | 2014 |
| Mehtaarts Ltd | Information & communication | 2025 |
| MEI Trans Ltd | Extraterritorial | 2017 |
| Meigui International Limited | Wholesale & retail | 2024 |
| Meiloon (UK) Limited | Administrative & support | 2004 |
| Meka Limited | Administrative & support | 2012 |
| Mekene Limited | Financial services | 2021 |
| Melendez Accounting Ltd | Professional & scientific | 2025 |
| Melis (MK) Limited | Real estate | 2026 |
| Mellor & Russell Direct Distribution Ltd | Wholesale & retail | 2016 |
| Mellor Wealth Ltd | Financial services | 2012 |
| Mellow Healthcare Ltd | Health & social care | 2011 |
| Melo Cleaning Ltd | Administrative & support | 2023 |
| Melodramatic Productions Ltd | Arts & recreation | 2010 |
| Melon Business Services Ltd | Professional & scientific | 2018 |
| Melrose Convenience Store Limited | Wholesale & retail | 2015 |
| Melsis Creations Limited | Information & communication | 2006 |
| Melster Services Ltd | Information & communication | 2022 |
| Melt & Mingle Ltd | Hospitality | 2025 |
| Melvfaith Ltd | Real estate | 2022 |
| Mema Stylist Ltd | Other services | 2022 |
| Membratech Limited | Construction | 2025 |
| Memento Audere Ltd | Hospitality | 2025 |
| Memoirofnature Ltd | Manufacturing | 2024 |
| Memories Events Ltd | Professional & scientific | 2023 |
| Memphis Motors Limited | Wholesale & retail | 2018 |
| Memsserp Ltd | Information & communication | 2015 |
| Men's Guild SA | Other services | 2019 |
| Mend Collective Ltd | Education | 2025 |
| Mendez Consulting Limited | Agriculture & fishing | 2013 |
| Meno Prop Ltd | Real estate | 2023 |
| Menopause Collective Ltd | Health & social care | 2022 |
| Mental Boxing Limited | Wholesale & retail | 2019 |
| Mentcare Ltd | Wholesale & retail | 2024 |
| Mentmore Capital Limited | Real estate | 2021 |
| Mentor Business Solutions Limited | Professional & scientific | 2005 |
| Mentoras Services Limited | Professional & scientific | 2021 |
| Mentri.Ai Ltd | Information & communication | 2025 |
| Menu-Hub Ltd | Administrative & support | 2022 |
| Menutic Limited | Hospitality | 2024 |
| Menzel Properties Limited | Real estate | 2016 |
| Meobo Limited | Wholesale & retail | 2024 |
| MEP Cleaning Services Ltd | Administrative & support | 2023 |
| Meraki Stony Stratford Ltd | Other services | 2019 |
| Merakie Homes & Investment Ltd | Real estate | 2022 |
| Meram Holdings Limited | Professional & scientific | 2024 |
| Meramide Limited | Information & communication | 2017 |
| Meranex Ltd | Information & communication | 2021 |
| Merble Valencia Limited | Real estate | 2019 |
| Mercedes-Benz Brooklands Limited | Real estate | 2004 |
| Mercedes-Benz Financial Services UK (Trustees) Limited | Financial services | 1996 |
| Mercedes-Benz Financial Services UK Limited | Financial services | 1990 |
| Mercedes-Benz Holdings UK Limited | Professional & scientific | 1973 |
| Mercedes-Benz Insurance Services UK Limited | Financial services | 1998 |
| Mercedes-Benz Parts Logistics UK Limited | Wholesale & retail | 2016 |