Over my year of ownership I've achieved an average of 47mpg (calculated by me, not the car. The car estimates around 4mpg higher).
And that's me trying to be efficient; so light throttle application, lots of coasting, not over-slowing for corners (that's the fun bit!). I only drive around once a week, usually on rural backroads, so no motorways and rarely dual carriageways.
I think i've read other say they get well above 50 when trying, so I'm probably not doing a good job.
My routes are usually quite hilly though which doesn't help. I noticed a decent drop in efficiency when I was doing a lot of journeys back and forth to my parents house, which has a particularly steep hill to navigate each way.