Victoria Garage Whitchurch Ltd: 162.9p a litre, 2.1 miles away. 2.0p a litre cheaper: saves £1.10 a tank, and costs about 77p of fuel to get there and back. Worth the trip.
On a 55-litre tank at 40mpg. The distance is straight-line rather than by road, so a real trip is longer than the one costed here.