| Flexitricity Limited | Aberdeen | 2004 |
| Flexymarty Ltd | London | 2025 |
| Flick Energy Ltd | Manchester | 2017 |
| Flimby Wind Energy Limited | London | 2005 |
| Flintly Power Limited | London | 2011 |
| Flinton Road Solar Limited | Cardiff | 2024 |
| Flip Energy Limited | Banbury | 2015 |
| Flipfinity Innovations Limited | Canterbury | 2014 |
| Flisher Energy Limited | Folkestone | 2014 |
| Flit Solar Park Limited | Exeter | 2013 |
| Floatricity Limited | Torquay | 2022 |
| Floergy Ltd | Woodford Green | 2025 |
| Flogas Natural GAS Ltd | Belfast | 2014 |
| Floods Ferry Wind Farm Limited | Harrogate | 2025 |
| Flooring Porter Limited | London | 2021 |
| Flooteg Ltd | Norwich | 2024 |
| Floral Energy Limited | Denmead | 2024 |
| Flores Energy Limited | London | 2017 |
| Florican Energy Limited | London | 2017 |
| Florida Energy Limited | Kingston Upon Thames | 2019 |
| Flotation Energy Limited | Edinburgh | 2018 |
| Flotta Wind Power Ltd | Glasgow | 2004 |
| Flow Energy Limited | Lichfield | 2011 |
| Flower Turbines Limited | London | 2025 |
| Flowpower Limited | Totnes | 2009 |
| Fluent Energy Limited | Crowborough | 2009 |
| Flynn Energy Ltd | Castlewellan | 2015 |
| Flyren Energy Ltd | London | 2017 |
| FM Electrical & Fire Alarm Services Ltd | London | 2018 |
| Fmac Group Limited | Hoddesdon | 1992 |
| Focap 2020 Limited | Weybridge | 2020 |
| Focus Multi Services Ltd | Southall | 2021 |
| Focused Hub Ltd | Downpatrick | 2017 |
| Foel Fach Wind Farm Limited | Maidenhead | 2022 |
| Folla Energy Ltd | Aberdeen | 2015 |
| Follands Folly Limited | Truro | 2011 |
| Folly Farm Energy Park Limited | London | 2023 |
| Folly Farm Solar Park Limited | London | 2014 |
| Folly Farm Solar Power Limited | High Wycombe | 2015 |
| Folly Lane Solar Limited | Gatwick, West Sussex | 2015 |
| Fonmon Solar Farm Limited | London | 2020 |
| Fonong OIL and GAS Ltd | Coventry | 2018 |
| FOOD2FUEL UK Ltd | London | 2026 |
| Footprint Zero Alpha Limited | London | 2023 |
| For-Jan Ltd | Peterborough | 2015 |
| Forbes Electrical Contractors Ltd | Glasgow | 2019 |
| Force 9 Energy Limited | Amersham | 2021 |
| Force Electrics Limited | Chichester | 2015 |
| Ford Energy Ltd. | Manchester | 2012 |
| Ford G2 Solar Farm Limited | Hove | 2014 |
| Forest Cooling Limited | Southampton | 2025 |
| Forest Estate Hydro Limited | Cheltenham | 2012 |
| Forestry Investment Ltd | London | 2024 |
| Forever Green Sun Ltd | Tonbridge | 2015 |
| Formisolis Ltd | London | 2025 |
| Formost Air-Conditioning Limited | Nottingham | 1997 |
| Forrester Electrical Limited | Manchester | 2013 |
| Forsa Energy (Beryl Street) Holdings Limited | Greenock | 2017 |
| Forsa Energy (Drumcross) Holdings Limited | Greenock | 2017 |
| Forsa Energy (Erskine) Holdings Limited | Greenock | 2017 |
| Forsa Energy (Spango) Holdings Limited | Greenock | 2017 |
| Forsa Energy CM Holdings Limited | Kirkby Lonsdale | 2017 |
| Forsa Energy GAS Acquisitions 2 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Acquisitions 3 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Acquisitions 5 Limited | Kirkby Lonsdale | 2022 |
| Forsa Energy GAS Acquisitions Holdco 1 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Acquisitions Holdco 2 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Acquisitions Holdco 3 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Acquisitions Holdco 4 Limited | Greenock | 2017 |
| Forsa Energy GAS Acquisitions Holdco 5 Limited | Kirkby Lonsdale | 2022 |
| Forsa Energy GAS Acquisitions Limited | Kirkby Lonsdale | 2017 |
| Forsa Energy GAS Intermediate 2 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Intermediate 3 Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy GAS Intermediate Limited | Kirkby Lonsdale | 2018 |
| Forsa Energy Holdings Limited | Kirkby Lonsdale | 2017 |
| Forsa Trading Limited | Greenock | 2023 |
| Forsinain Forest Wind Farm Limited | London | 2023 |
| Forss Energy Storage Limited | Huntingdon | 2022 |
| Fortescue UK IP Limited | Edinburgh | 2023 |
| Fortex Fire & Security Ltd | Ballynahinch | 2019 |
| Forthwind Limited | Burntisland | 2014 |
| Fortify Smart Grid Ltd | Leamington Spa | 2025 |
| Fortis Energy Limited | Ryde | 2009 |
| Fortis Renewable Energy Limited | London | 2011 |
| Fortress Fuel Ltd | London | 2026 |
| Fortress Renewables Limited | London | 2023 |
| Fortum Glasgow Limited | Reading | 2016 |
| Fortune AF Co Ltd | London | 2025 |
| Forward Renewables Ltd | Cheltenham | 2021 |
| FOS Technology UK Ltd | Gateshead | 2024 |
| Fosse Green Energy Limited | London | 2021 |
| Fosse Thermal and Sheet Metal Ltd | Leicester | 2014 |
| Fossilyse Ltd | London | 2024 |
| Foster Energy Ltd | Bromsgrove | 2022 |
| Foula Electricity Company Ltd | Shetland | 2024 |
| Four Burrows Limited | London | 1994 |
| Four Burrows Solar Park Limited | Exeter | 2012 |
| Four Counties Air Conditioning Ltd | Atherstone | 2019 |
| Four Crosses Solar Limited | London | 2025 |
| Four Seasons AC Ltd | Brentwood | 2024 |