As now it seems like the £1 a litre has long gone and old enough to remember when the price was displayed in good old gallons and not litres here is a site i think might help ......http://www.petrolprices.com
When you register it will monitor prices near you postcode and send the prices to your inbox. I have found prices locally can vary substantially
I hope you find it usefull if like me i am sick of paying all that duty to Mr Brown and chums!!
P.s If you are driving to France currently Fuel is about 11p a litre cheaper have a look at the Auchan supermarket website it displays there current petrol station prices!