| MEHDI22 Limited | Hospitality | 2017 |
| Mehra and Trading Company Limited | Wholesale & retail | 2025 |
| Mein Renovation Limited | Construction | 2023 |
| MEL Care Ltd | Health & social care | 2019 |
| Mela Decorators Ltd | Construction | 2025 |
| Melanie Hunter Marketing Limited | Professional & scientific | 2017 |
| Melgeo International Ltd | Wholesale & retail | 2024 |
| Melior Joinery Ltd | Manufacturing | 2024 |
| Melksham Car Sale and Tyre Centre Ltd | Wholesale & retail | 2025 |
| Melksham Car Wash Ltd | Administrative & support | 2020 |
| Meltry Limited | Health & social care | 2018 |
| Melville and Hill Properties Limited | Real estate | 2023 |
| Mem-Star Distribution Ltd | Wholesale & retail | 2014 |
| Memory Squared Ltd | Information & communication | 2024 |
| Mendaq Limited | Financial services | 2024 |
| Mendes Swindon Ltd | Hospitality | 2021 |
| Mendie Golf Ltd | Wholesale & retail | 2019 |
| Meols Projects Services Ltd | Mining & quarrying | 2011 |
| Meraid Ltd | Wholesale & retail | 2023 |
| Merakitanningandbeauty Limited | Other services | 2024 |
| Mercatoria UK Ltd | Professional & scientific | 2026 |
| Mercetto Hub Limited | Wholesale & retail | 2025 |
| Merchiston Pharma Limited | Wholesale & retail | 2022 |
| Mercury Paraplanning Limited | Financial services | 2015 |
| Mercutio Leisure Limited | Hospitality | 2016 |
| Mercy Cleaners and Removers Ltd | Administrative & support | 2024 |
| Mercynik Naija Foods and Bakes Limited | Hospitality | 2026 |
| Meridian Blue Healthcare Limited | Health & social care | 2020 |
| Meridian Lifestyle Limited | Professional & scientific | 2025 |
| Merimaya Ltd | Health & social care | 2023 |
| Merit Healthcare Ltd | Health & social care | 2015 |
| Merk Properties Limited | Real estate | 2023 |
| Merlong Services Limited | Professional & scientific | 2009 |
| Merrison Robert Donald 80530 Limited | Transport & logistics | 2014 |
| Merula Marketing Ltd | Administrative & support | 2024 |
| Metabox Tech Ltd | Information & communication | 2024 |
| Metal ION Solutions Ltd | Professional & scientific | 2021 |
| Metaldance Limited | Manufacturing | 1997 |
| Metalite Engineering Company Limited | Manufacturing | 1973 |
| Metamorphosis Construction Ltd | Construction | 2025 |
| Metaportal Limited | Information & communication | 2017 |
| Method Consulting Engineering Ltd | Professional & scientific | 2019 |
| Method Consulting LLP | | 2011 |
| Metoceanology Limited | Professional & scientific | 2012 |
| Metric Group Holdings Limited | Financial services | 1997 |
| Metric Group Limited | Manufacturing | 1990 |
| Metric Tristar Limited | Manufacturing | 2025 |
| Metrifix Ltd | Construction | 2026 |
| Metron Growth Ltd | Information & communication | 2022 |
| Metropolitan Optical Company Limited | Professional & scientific | 2002 |
| Mexim Transport Ltd | Transport & logistics | 2025 |
| Meysey Technology Limited | Information & communication | 2023 |
| MF Engineering Services Limited | Professional & scientific | 2024 |
| MF Martial Arts East Midlands Ltd | Education | 2023 |
| MF Nurseries and Childcare Limited | Health & social care | 2024 |
| MFH Real Estates Ltd | Real estate | 2024 |
| MFJ! Ltd | Administrative & support | 2019 |
| Mfjbuildings Ltd | Construction | 2024 |
| Mfsc Consultancy Limited | Professional & scientific | 2015 |
| MG Beauty&Aesthetics Limited | Health & social care | 2025 |
| MG Refrigeration Ltd | Manufacturing | 2024 |
| MGA Roofing Contractors Limited | Construction | 2023 |
| MGA Speed Ltd | Transport & logistics | 2026 |
| MGA582 Ltd | Hospitality | 2025 |
| MGE Services Limited | Manufacturing | 1996 |
| MGF Facilities Management Services Ltd | Administrative & support | 2021 |
| Mgupysule Limited | Health & social care | 2022 |
| MH93 Ltd | Arts & recreation | 2024 |
| MHD Partnership Limited | Administrative & support | 2000 |
| Mhlz Ltd | Real estate | 2023 |
| MHP Medical Healthcare Professionals Ltd | Health & social care | 2014 |
| MI Telecom Services Ltd | Professional & scientific | 2023 |
| Mia&Dom Transport Ltd | Transport & logistics | 2021 |
| Miab Healthcare Ltd | Health & social care | 2021 |
| Miah Bros Swindon Ltd | Wholesale & retail | 2017 |
| Miah Pharma Ltd | Other services | 2019 |
| Miah's Kitchen Swindon Ltd | Hospitality | 2018 |
| Miatta Care Ltd | Health & social care | 2019 |
| Michael Batt Holdings Limited | Real estate | 2017 |
| Michael Jacob Cars and Collectables Ltd | Wholesale & retail | 2025 |
| Michael Mash Limited | Professional & scientific | 2007 |
| Michael Paul Carpets & Flooring Ltd | Construction | 2015 |
| Michael Reynolds Hairdressing Limited | Other services | 2003 |
| Michael's Workwear Limited | Wholesale & retail | 2009 |
| Michelle Valerie Ltd | Construction | 2025 |
| Michelle's Cleans Ltd | Administrative & support | 2022 |
| Michu Art Studio Ltd | Professional & scientific | 2025 |
| Mickeus Ltd | Real estate | 2024 |
| Mico 24 Ltd | Transport & logistics | 2012 |
| Microflow Products Ltd | Professional & scientific | 2024 |
| Midas Contracting Solutions Limited | Professional & scientific | 2024 |
| Midas One Limited | Information & communication | 2024 |
| Middleton Solutions Ltd | Administrative & support | 2017 |
| Mignonne Apparel Limited | Manufacturing | 2025 |
| Migona Limited | Wholesale & retail | 2021 |
| Miguelangelo Limited | Transport & logistics | 2015 |
| Mike Heal Joinery Ltd | Construction | 2016 |
| Mike Victor Limited | Wholesale & retail | 2012 |
| Miki Logistic Ltd | Transport & logistics | 2024 |
| Milan Pro Ltd | Construction | 2020 |