| First Call Electrical Services Ltd | Construction | 2020 |
| First Choice (Turkey) Limited | Real estate | 1988 |
| First Choice City Accommodation Ltd | Real estate | 2022 |
| First Choice FM Ltd | Administrative & support | 2020 |
| First Choice Holiday Hypermarkets Limited | Administrative & support | 1998 |
| First Choice Holidays & Flights Limited | Other services | 1979 |
| First Choice Holidays Finance Limited | Financial services | 2000 |
| First Choice Holidays Limited | Financial services | 1896 |
| First Choice Properties Group Ltd | Households | 2024 |
| First Choice Tours Ltd | Other services | 2021 |
| First Clarity Limited | Information & communication | 2006 |
| First Class Autos Luton Ltd | Wholesale & retail | 2023 |
| First Class Care Services Limited | Administrative & support | 2017 |
| First Class Cars Chauffeurs Ltd | Transport & logistics | 2016 |
| First Class Cars Worldwide Ltd | Professional & scientific | 2004 |
| First Class Housing & Support Ltd | Real estate | 2019 |
| First Class Roofer Ltd | Construction | 2024 |
| First Contact Physio Ltd | Health & social care | 2021 |
| First Defence Consulting Ltd | Other services | 2022 |
| First Light Maintenance Ltd | Construction | 2025 |
| First Logick Ltd | Information & communication | 2024 |
| First Pass Drive Ltd | Education | 2024 |
| First Rental Limited | Extraterritorial | 1998 |
| First Response Heating and GAS Ltd | Construction | 2024 |
| First Response Investment Group Ltd | Real estate | 2024 |
| First Steps Learning Limited | Education | 2011 |
| First Strategy Financial Services Ltd | Financial services | 2016 |
| First Time Care Limited | Transport & logistics | 2020 |
| First-Temp Limited | Administrative & support | 2018 |
| Firstforpharma Ltd | Wholesale & retail | 2020 |
| Firstmile Logistics Limited | Wholesale & retail | 2024 |
| Fiscal Connect Ltd | Professional & scientific | 2025 |
| Fiscal Umbrella Accountancy Services Limited | Professional & scientific | 2025 |
| Fiscal Umbrella Limited | Professional & scientific | 2025 |
| Fish Property Luton Ltd | Real estate | 2016 |
| Fishnstuff Ltd | Hospitality | 2024 |
| Fistco (UK) Ltd | Professional & scientific | 2012 |
| Fit PV Ltd | Construction | 2026 |
| FITNESS4U Gym CIC | Arts & recreation | 2014 |
| Fitnfreshuk Ltd | Hospitality | 2019 |
| Fitsmart Solutions Limited | Construction | 2025 |
| Fittville (UK) Limited | Education | 2005 |
| Five Akhis Luton Ltd | Hospitality | 2025 |
| Five Autos Limited | Wholesale & retail | 2025 |
| Five Chimneys Ltd. | Construction | 2016 |
| Five E International UK Ltd | Manufacturing | 2010 |
| Five OL Ltd | Transport & logistics | 2023 |
| Five Pillar Projects CIC | Health & social care | 2024 |
| Five Secretaries Ltd. | Administrative & support | 1998 |
| Five Star Barbers Luton Ltd | Other services | 2018 |
| Five Star Demolition Limited | Construction | 2014 |
| Five Star Hair Dresser Limited | Other services | 2017 |
| Five Twos Travel Limited | Transport & logistics | 2017 |
| Fivestar Chauffeur Services RC Ltd | Other services | 2024 |
| Fixaura Ltd | Wholesale & retail | 2025 |
| Fixen Ltd | Construction | 2025 |
| Fixfix Limited | Wholesale & retail | 2025 |
| Fixitfast Tech Limited | Other services | 2025 |
| Fixology Ltd | Information & communication | 2022 |
| Fixoo Venture Limited | Wholesale & retail | 2023 |
| FIZ Restaurant Ltd | Hospitality | 2025 |
| Fizzah Cars Ltd | Wholesale & retail | 2024 |
| Fjas R Ltd | Professional & scientific | 2018 |
| Fjell AS Ltd | Wholesale & retail | 2025 |
| FJR Bill Ltd | Other services | 2026 |
| FK Plumbing & Heating Engineering Services Ltd | Construction | 2018 |
| FK Utilities Ltd | Construction | 2018 |
| Fkca Limited | Professional & scientific | 2005 |
| FKR Consultancy Limited | Information & communication | 2013 |
| Flaag Group Ltd | Financial services | 2017 |
| Flamefix Heating Solutions Ltd | Construction | 2025 |
| Flamers Luton Limited | Hospitality | 2022 |
| Flamez Ltd | Hospitality | 2026 |
| Flaming Grill Luton Ltd | Hospitality | 2025 |
| Flamingos Property Consulting Limited | Real estate | 2010 |
| Flare TEC Media Ltd | Information & communication | 2024 |
| Flaring Ltd | Wholesale & retail | 2025 |
| Flat CAP Estates Limited | Real estate | 2015 |
| Flatbase Construction Services Limited | Construction | 2004 |
| Flava Kitchen Limited | Hospitality | 2023 |
| Flava Luton Ltd | Hospitality | 2021 |
| Flava Sensei Ltd | Hospitality | 2025 |
| Flava Sundon Limited | Hospitality | 2026 |
| Flavour Haven Ltd | Hospitality | 2023 |
| Flavy Ltd | Transport & logistics | 2017 |
| Flawless London Limited | Health & social care | 2018 |
| Fleably Solution Limited | Professional & scientific | 2025 |
| Fleetx Limited | Transport & logistics | 2024 |
| Fleurette Ltd | Administrative & support | 2023 |
| Flex Removal Ltd | Transport & logistics | 2019 |
| Flex Security Ltd | Transport & logistics | 2020 |
| Flexelles Ltd | Real estate | 2021 |
| Flexi Care Physio Limited | Health & social care | 2024 |
| Flexi Medico Limited | Health & social care | 2017 |
| Flexi Recruit Solutions Ltd | Administrative & support | 2019 |
| Flexing Partners Limited | Administrative & support | 2025 |
| Flexipay Group Ltd | Transport & logistics | 2016 |
| Flexipower (Holdings) Limited | Administrative & support | 2008 |
| Flexlet Management Ltd | Real estate | 2025 |
| Flexplus Limited | Other services | 2023 |