We did a weekend trip to Alton Towers recently. 155 miles each way, plus two trips to the local Travellodge. In total it was 340 miles and we used 3/4s of a tank of petrol. That's approx. 37.5 litres. It's common to see the fuel consumption showing over 60mpg on motorways. The trip-computers, which I don't often reset show over 38mpg averaged over thousands of miles of 'normal' combined driving. The car has a very low drag and once you get used to it, you find you can coast up to junctions from a long way back. There's very little 'engine breaking'. At first, speed cameras will give you a scare as you seem to roll into them without slowing down, but you get used to it eventually. The Michelin 'Energy Saver' tyres are the lowest friction rating available, and you can really tell the difference. It's far better on fuel than my daughter's 1.2 Clio, yet feels far more powerfull.
Finally got the new wheels on my GT line, Fox Racing FX004, from Wheelbase in Oldham in and out in less than 1 hour with the tyres swapped over, same size/offset as standard but in my opinion, a lot better looking !