I got 46mpg on a 140km autobahn run in quite heavy traffic with an average speed of 97kph. I have got 8.1 litres/100km (35mpg) over the first 1700kms.
What is clear if you drive carefully, then you may get near VW's claimed figures. But drive a GTi like a GTi and expect sub-30MPG figures. That crackle when the DSG shifts up under power is addictive.
In round figures I'm getting about 9 litres/100km (31mpg) around town and 6.5 litres (43mpg) on a run.
I recently did a 600km Swiss Autobahn round trip, where the speed limit is 120kph. It took me just under 3 hours each way, average speed around 100kph (62mph) with ACC set to 125kph (77.6mph),
Going I used Eco mode exclusively and got 6.7 litres per 100km (42mpg) on my return I used Comfort and got 6.5l/100km (43mpg)...