Thats a bit to much for me most of my driving is town driving and I do have to make some kind of sensible decision.
If "most of your driving is town driving", then surely your annual milage is low. So it matters not if you average 15MPG or 25MPG, if you do diddly squat milage then the costs are low regardless.
Somehow I don't see a BMW being the car for you if you are put off by such meager things as fuel cost.