First change your electricity provider:

 http://www.unit-e.co.uk/

Unit[e] are the only UK electricity provider that guarantee 100% renewable generation - they only own hydro and wind turbines. You pay slightly more than you would with n-power et al (about 10% more to be exact) but surely another £8ish per quarter is worth the peace of mind of knowing that your money is only going to support renewable power sources?

Secondly, if you drive a diesel car, change over to biodiesel:

Make you own from discarded chip-fat (and don't pay fuel tax if you want to be a war-tax resistor):
 http://www.veggiepower.org.uk/

Buy it legally (be a law abiding wimp):
 http://www.biodiesel.co.uk/
 http://www.biofuels.fsnet.co.uk/biobiz.htm
 http://www.biodieselfillingstations.co.uk/outlets.htm

Don't believe it works?
 http://www.mauibiodiesel.org/testimonials.htm

Nearly all diesel engines (just google your make and model with the word "biodiesel" to check for reports on your car) can run on virtually any type of biological oil (cooking oils to me and you!). This is much better for the environment than fossil fuels because the carbon in veggie-oil is already in the carbon cycle and is not contributing to an increase in global warming. We should leave those filthy fossilised oils where they belong - in the ground! Forget putting a tiger in your tank - put a sunflower in it!

Only grass-roots effort can stop this environmental destruction and endless resource-wars - vote with your wallets people!