• Amerada
• Atlantic Electric and Gas
• Basic Power
• British Gas
• Cambridge Gas and Electricity
• Countrywide Energy
• Ecotricity
• EDF Energy
• E.ON Energy
• Equipower (EBICo)
• Good Energy
• Green Energy UK
• London Energy
• Lloyds TSB
• Manweb
• npower
• Sainsburys Energy
• Scottish Hydro-Electric
• ScottishPower
• Seeboard Energy
• Southern Electric
• Swalec
• SWEB Energy
• Utility Warehouse
• Utilita
• Virgin Energy
• ZEST4
• Other
• None
• None (Off Grid)

Source: http://www.electricity-guide.org.uk/companies.html