My main car is a Citroen C1, which is mechanically identical to George. I haven't got so many bells and whistles (no satnav, no aircon) but I do have a rev counter
I've kept brim-to-brim figures for each tank since I bought it in December 2008. I've covered just over 46000 miles in that time. The average economy over that time has been 56.46mpg, although I was getting an average of 60mpg in the first year before I moved house (my commute is now shorter and hillier). My best tank has been 517 miles from 35.93 litres, which is 65.4mpg (UK mpg).
Here is a graph of my economy (axis on the right is tank economy in UK mpg). Gaps are where I haven't brimmed it for a while, and low points are where I've misbehaved for some or all of the tank and driven too fast! You can see the seasonal variation, especially in 2009, and you can see it hasn't been as good since I moved house in February 2010.