There have been plenty of people getting 40mpg ave, 45mpg ave and 50+mpg ave. People's driving styles and commutes are different. I have found with mine that with journeys under 15 miles, the mpg suffers.
If I were to do a 15 mile commute, I would see 50mpg with my driving style, 12 mile commute (my actual) is about 46mpg with no regens and 41mpg when it is regenning (44mpg total combined). I would expect a 10 mile commute would see me dip to 40mpg average and more regens than I currently get.
One thing for sure with the GTD is that 55mpg + is extraordinary for the average jouney. The official figures are fantasy, inflated by 20% over the previous generation because the testing regime has changed, not because VAG engines have come on in leaps and bounds. Every other marque out there (Ford/Mazda/Vauxhall/BMW etc) has also seen 20% increases in their published economy over the last 12 months or so on new models - that is no coincidence or simultaneous engineering improvement.