My daily commute's very similar to this, but I do an extra 2 miles on top of yours. I use £30 a week on £1.29 p/l BP Ultimate, not entirely sure of the MPG as my computer's still in Japanese mode lol & only does Kilometres per pint or something but that's usually between 7.6-9
Fuelled up beginning of this week at a different station to my normal one, still only a few miles away though. Almost had a heart attack when I saw the price - £1.49 PER LITRE!!!!!! 20p more, both BP, separated by a couple of miles . . . .