Green Electricity
FIRST GET A SMART METER _ IT IS FREE!!
Buy Green Electricity.
http://www.greenelectricity.org/
http://www.ethicalconsumer.org/buyersguides/energy/greenelectricitysuppliers.aspx
Even Better, Have Solar PV Panels, A Heatpump or A Wind Mill installed; The government have support schemes:
http://www.energysavingtrust.org.uk/renewable-energy/electricity/solar-panels