The BBC have a nice graphic to cover the story of petrol reaching a new high
So, fuel duty is about half of the price. Bear in mind that Fuel Duty is entirely within the control of the British government. Whilst the wholesale cost is at the mercy of OPEC and the dollar/sterling exchange rate, the majority of the high price is because of the government.
At any moment they could cut fuel duty if only the government didn't pish so much money up the wall. They get £26,000,000,000 from fuel duty, about 6% of the £400,000,000,000 total estimated tax receipts for 2010.