Indeed, my dad has been filling up recently. Sainsburys and Tesco seems to be the cheapest.
Don't know.. what with the new Morissons promotion.
"Spend £60 on shopping and get a voucher for 12p/lt off fuel"

Think about this.
They spend a fortune on new pumps. Pumps that speed up the fuel dispensing process because you can pay by card at the pump. Flowthrough of cars and drivers is improved because drivers no longer have to go and queue for that one till in the forecourt shop.
.
Then...
.
They start a voucher promotion that means you have to go into the forecourt shop, because you can't redeem the voucher at the pump.
This a.m. you couldn't get to our local Morissons. The access road to the supermarket was blocked by the overflowing queues into the service station. The garage over the road had one or two cars at the pumps....