My remapped MK5 will do 27-29 around town. 30 - 35 on the motorway (all depending on how much of a rush I'm in).
I've done several journeys op norf recently and sat at 80 - 85 and only just sneaked into the 30s. Sit at 70 and you'll get 34-35 easily.
As Chuff very rightly says, GTI shouldnt be driven with MPG in mind. First year of owning her I used to keep it the trip comp on the MPG reading. Now I try not and just enjoy the car and fill her up when she needs it. Still check it now and again thought to make sure we are all ok lol

Just try and enjoy her.