Had my MK4 TDI Cupra almost 6 months now and do a round trip to and from work of about 45 miles, with a good mix of country/dual carriageway/traffic jams. Get about 45-47mpg over the journey. My aim is always 50mpg after the first 10m (only about 30-39 for the first 8 till it warms up!) due both to the traffic and to allow the oil to warm up, which often happens due to slow traffic. Then normally floor it to 110-120 leptons as I am normally late(which are not mph and have been covered before!
! On a short day-time trip I get much less but I think the computer measures things differently from other cars - my girlfriends Fiat Punto (1.2 litre) will read 51-53mpg over the first 5 miles but I have driven to Scotland in both and got 3mpg (52mpg:49mpg) more in the Beeza! Even so, my second mileage counter still reads only approx 43mpg for the last 100 hrs. Much better than my last car (Honda civic), but not as good as I thought it would be. Must be my driving!