To get max MPG you just have to go easy on the acceleration, or don't brake. When my wife drives the 156, she gets much better mileage than I do because she coasts up to stops, and doesn't often actually stop the car. She still belts along, but gets there more gradually.
Also if you are in stop start traffic, or do short journeys only, you are stuffed. If in a fortnight I only drive the journey to and from work which is about 6 or 7 miles, I will kill £20 of fuel in about 80-100 miles. If my wife drives a loing way, say a couple of hundred miles, she can squeeze about 400 miles out of £55 (which is in the bottom of the guage a fair bit to be fair!)