| GAS and Power Solutions Limited | Durham | 2021 |
| GAS and Sparks Ltd. | Twickenham | 2017 |
| GAS Boiler Experts Ltd | London | 2019 |
| GAS Care Inverclyde Ltd | Greenock | 2019 |
| GAS Direct (London) Limited | Kent | 2014 |
| GAS Generation Coatbridge Limited | Norwich | 2016 |
| GAS Generation Forfar Limited | Norwich | 2017 |
| GAS Generation Oldham Limited | Norwich | 2016 |
| GAS Generation Thurrock Limited | Norwich | 2016 |
| GAS Ireland Ltd | Belfast | 2016 |
| GAS Maintenance Heating Limited | Surrey | 2007 |
| GAS Manufacturing Limited | Llanelli | 2007 |
| GAS Nation Ltd | Birmingham | 2023 |
| GAS Network Maintenance Services Limited | Ulverston | 2022 |
| GAS Plus Supply Limited | London | 2004 |
| GAS Repair Ltd | Billericay | 2017 |
| GAS Safe Bristol Ltd | Bedminster | 2007 |
| GAS Safe Services (Greenock) Limited | Gourock | 2014 |
| GAS Tech LPG Limited | Guildford | 2024 |
| GAS Trap Ltd | Romford | 2021 |
| GAS Tune Ltd | Ipswich | 2020 |
| GAS, GAS, GAS Heating and Plumbing by Kevin Hough Ltd | Alfreton | 2021 |
| GAS2WIRE (G2W) Ventures Limited | Manchester | 2018 |
| Gasbros Ltd | London | 2025 |
| Gascoigne Wood Power Limited | Bedford | 2016 |
| Gascool Air Conditioning Limited | | 2004 |
| Gascorp (Plaxton) Limited | London | 2017 |
| Gascorp Ltd | Bradford | 2018 |
| Gasflow Limited | Northampton | 1997 |
| GASFLOW4U Ltd | London | 2024 |
| Gasguard Ltd | London | 2024 |
| Gask Energy Limited | Edinburgh | 2014 |
| Gasline Ltd | Newport Pagnell | 2014 |
| Gasol LNG Import Limited | Birmingham | 2013 |
| Gasprompt Limited | Leigh On Sea | 2014 |
| Gasrec Ltd | London | 2003 |
| Gastec Staffs Ltd | Stoke-On-Trent | 2025 |
| Gastec Stoke Ltd | Stoke-On-Trent | 2023 |
| Gastex Plumbing & Heating Services Ltd | Dorchester | 2016 |
| Gaswyse Ltd | Sheffield | 2019 |
| GAT Utilities Limited | Colchester | 2025 |
| Gate Burton Energy Park Limited | Houghton Le Spring | 2020 |
| Gateshead Electric Forecourt Ltd | Swindon | 2019 |
| Gateshead Energy Company Limited | Gateshead | 2015 |
| Gatesway Solar Limited | Potters Bar | 2013 |
| Gatford Plumbing Ltd | Portsmouth | 2018 |
| Gatwick Electric Forecourt Ltd | Swindon | 2020 |
| Gaudie & Muir Limited | Holm | 2012 |
| Gaulcross Wind Limited | Banff | 2015 |
| Gaultney Solar Park Limited | Exeter | 2014 |
| Gauntlet Properties Limited | Newmarket | 2006 |
| Gaussian Power Limited | London | 2022 |
| GAV Warwick Ltd | Gateshead | 2009 |
| Gavanna Electrical Contractors Limited | Inverness | 2015 |
| Gawcott Fields Community Solar Project C.I.C. | Redruth | 2015 |
| Gawnsmoss Energy C.I.C. | Banff | 2015 |
| Gayton Solar Limited | Reading | 2022 |
| Gazelle Ventures Designs Limited | Rickmansworth | 2021 |
| Gazpro Ltd | London | 2024 |
| GB Developers Limited | Middlesbrough | 2002 |
| GB Energy (Leadburn) Limited | Penicuik | 2016 |
| GB Flexible Power Limited | Bristol | 2014 |
| GB Hvac Ltd | Christchurch | 2018 |
| GB Wind Farm Limited | London | 2023 |
| Gb-Bio Limited | London | 2006 |
| GB4 Mechanical Ltd | Dudley | 2024 |
| GBC Electrical Contractors Ltd | High Wycombe | 2020 |
| GBE Electrical Contractors Limited | Callington | 2009 |
| Gbe-N (Warrington) Limited | Warrington | 2025 |
| Gbpv Holdings Limited | Stroud | 2021 |
| Gbsl Dorking Limited | London | 2016 |
| GBW Supplies UK Ltd | Betchworth | 2014 |
| GC Brokerage Limited | London | 2009 |
| GC Plumbing & Heating (NE) Ltd | Hartlepool | 2016 |
| Gcms Facility Management Ltd | Hull | 2020 |
| GCP Generation Ltd | Warrington | 2016 |
| GCT Technologies Limited | London | 2012 |
| Gcud Limited | London | 2018 |
| GD Electrical Ltd | Penrith | 2015 |
| GD001 Limited | Beverley | 2024 |
| GD002 Limited | Beverley | 2024 |
| GD003 Limited | Beverley | 2024 |
| GD004 Limited | Beverley | 2024 |
| GD005 Limited | Beverley | 2024 |
| GD006 Limited | Beverley | 2024 |
| GD007 Limited | Beverley | 2024 |
| GD008 Limited | Beverley | 2024 |
| GD009 Limited | Beverley | 2024 |
| GD010 Limited | Beverley | 2024 |
| GDE Electrical Ltd | Croydon | 2023 |
| Gdelecrico Limited | Corby | 2025 |
| GDF Suez Teesside Limited | Manchester | 1990 |
| GDM Gillwald Electrical Limited | London | 2004 |
| GDS Yarnton Ltd | London | 2014 |
| GEB Power Limited | Middlesbrough | 2008 |
| GEC Power Limited | Newcastle Upon Tyne | 2021 |
| Gecko Renewables Ltd | Pudsey | 2019 |
| Geco Renewables Limited | Bristol | 2016 |
| Gedling Solar Limited | London | 2012 |
| Gedulah Solar Limited | Exeter | 2014 |