| Menlo Bark Ltd | Administrative & support | 2024 |
| Menlo Park Recruitment Ltd | Financial services | 2021 |
| Meno Diaries Ltd | Other services | 2021 |
| Menon Anaesthetics Ltd | Health & social care | 2013 |
| Menovia Ltd | Information & communication | 2025 |
| Menstone Limited | Real estate | 2015 |
| Menstylegroup Limited | Other services | 2017 |
| Mentalworkz Limited | Information & communication | 2015 |
| Mentools Ltd | Information & communication | 2023 |
| Mentor Education Limited | Education | 2012 |
| Mentorspring Ltd | Education | 2025 |
| Menu-Uk Ltd | Information & communication | 2022 |
| MEP & Sons Limited | Real estate | 2026 |
| MEP Facility Management Ltd | Wholesale & retail | 2024 |
| MEP Quantity Surveying Services Ltd | Professional & scientific | 2026 |
| MEP Range Ltd | Wholesale & retail | 2005 |
| MEQ Realisations Limited | Professional & scientific | 2004 |
| MER Skipton Ltd | Hospitality | 2021 |
| Meraadil Ltd | Wholesale & retail | 2025 |
| Meraki Therapy Limited | Health & social care | 2023 |
| Mercantile Trading Ltd | Wholesale & retail | 2024 |
| Mercer Conversions Ltd | Manufacturing | 2025 |
| Mercer Richardson & Partners Limited | Administrative & support | 1997 |
| Merch & Mindz Limited | Wholesale & retail | 2025 |
| Merch by Team Ltd | Wholesale & retail | 2026 |
| Merch Stall Ltd | Manufacturing | 2021 |
| Merch Street Limited | Wholesale & retail | 2025 |
| Merchant Adventurer Limited | Financial services | 2021 |
| Merchant Link Ltd | Information & communication | 2025 |
| Merchant Technology Marketing Limited | Professional & scientific | 2009 |
| Merchants House Management (Leeds) Limited | Households | 1999 |
| Merchants' Quay Management Company Limited | Households | 1999 |
| Mercia Regen AG Co Ltd | Financial services | 2024 |
| Merco Medica Limited | Construction | 2017 |
| Mercury Print & Packaging Ltd. | Manufacturing | 1999 |
| Mercury Property Maintenance Limited | Construction | 2016 |
| MERCURY3 Consult Ltd | Professional & scientific | 2017 |
| MERCURY3 Holdings Limited | Financial services | 2021 |
| Mercy Global Consult Ltd. | Professional & scientific | 2011 |
| Mercy Global Properties Solutions Ltd | Real estate | 2012 |
| Mereb Properties Yorkshire Limited | Real estate | 2024 |
| Meredith Tax Advice Ltd | Administrative & support | 2013 |
| Meredith Tax LLP | | 2010 |
| Meridian Accommodation Limited | Hospitality | 2021 |
| Meridian Furnishings Limited | Manufacturing | 2020 |
| Meridian Interface Ltd | Information & communication | 2024 |
| Meridian Properties (Leeds) Ltd | Real estate | 2009 |
| Meridian Strategic Advisory Limited | Professional & scientific | 2026 |
| Meridian Work Surfaces Limited | Manufacturing | 2010 |
| Merit Process Systems Limited | Manufacturing | 2017 |
| Merite Healthcare Solutions Limited | Health & social care | 2021 |
| Merke Limited | Professional & scientific | 2021 |
| Merkel Properties Ltd | Real estate | 2025 |
| Merlin Embedded Limited | Information & communication | 2023 |
| Merlin Holiday Homes Limited | Real estate | 2020 |
| Merlin Imaging Limited | Health & social care | 2017 |
| Merlin PTY Limited | Real estate | 2022 |
| Merlinsoft Limited | Information & communication | 2013 |
| Merner Estates Limited | Real estate | 2024 |
| Merrion Centre Limited(The) | Real estate | 1964 |
| Merrion House Limited Liability Partnership | | 2013 |
| Merry Hoover Cleaning Services Ltd | Other services | 2016 |
| Merry Nails & Beauty Limited | Other services | 2025 |
| Merryevent Limited | Professional & scientific | 2012 |
| Merrylee Road Developments Limited | Construction | 2024 |
| Mersey View Limited | Wholesale & retail | 2025 |
| Mersin Shawarma Restaurant Limited | Hospitality | 2024 |
| Mertek IT Solutions Ltd | Information & communication | 2015 |
| Merve Ltd | Information & communication | 2025 |
| Merydian Placement Partners Ltd | Health & social care | 2026 |
| Mesavvy Ltd | Financial services | 2025 |
| Mesh Architects Limited | Professional & scientific | 2017 |
| Mesh Cleaning Services Limited | Administrative & support | 2026 |
| Meshebah Community Interest Company | Wholesale & retail | 2023 |
| Meshplatform Ltd | Information & communication | 2025 |
| Mesk Holdings Ltd | Real estate | 2025 |
| Meson Electrical Services Limited | Construction | 2006 |
| Meson Engineering Services Limited | Manufacturing | 2018 |
| Mess Propco Ltd | Real estate | 2023 |
| Messages in Motion Limited | Wholesale & retail | 1989 |
| Messer Technology Co., Ltd | Wholesale & retail | 2021 |
| Mestech Limited | Information & communication | 2025 |
| MET Consultancy Ltd | Professional & scientific | 2017 |
| MET Engineers Ltd | Professional & scientific | 2011 |
| MET Geoenvironmental Limited | Professional & scientific | 1998 |
| MET Geoinfo Limited | Information & communication | 2008 |
| MET Group Ltd | Construction | 2018 |
| MET PAK Limited | Manufacturing | 2014 |
| MET Partners Ltd | Administrative & support | 2011 |
| MET Trading Limited | Mining & quarrying | 2010 |
| Met-Fab Developments Limited | Real estate | 2014 |
| Met-Fab Solutions Limited | Manufacturing | 2009 |
| Meta Virtual Estates Limited | Real estate | 2022 |
| Metabolic Healthcare Ltd | Health & social care | 2015 |
| Metafora Search Limited | Administrative & support | 2025 |
| Metahealth Ltd | Health & social care | 2024 |
| Metal Cabinet Sales Holdings Limited | Financial services | 2026 |
| Metal Formers Limited | Manufacturing | 1968 |
| Metal Talent Solutions Ltd | Administrative & support | 2026 |
| Metalhand Attachments Ltd | Wholesale & retail | 2019 |