Our local BP (Australia) had unleaded 91 octane with a splash of alcohol for AU$1.15, diesel was AU$1.22. Tax is about 60% of the selling price - we pay excise tax and then they add GST (VAT) to the excise selling price - talk about taxing a tax. AU$1 = about UK 60 pence.
Big weekly cycle differences in retail price - cheapest days are Wednesdays and Thursdays, most expensive Friday to Sunday. Been like that for years due to higher demand on weekends for petrol.
When I worked in fuel distribution we tried all sorts of things to try and even out demand so that we did not have fuel terminals and fleets idle for three days and then over used for four days. It always came back to pricing at the pump which encouraged 50% of the population to buy when it was cheap and the other 50% to buy when they had an empty tank.