I've got a 1.8T which has been remapped by Revo and has a full stainless exhaust (sports cat), and was dyno'd at 229BHP. My trip to work is 30 miles and I can get, at best 41MPG but that's driving like a nun... If i have a little squirt now and then i average out at around 34MPG.
I picked up an SPS1 off Ebay a few weeks ago. When the mapping is set to factory standard, I get about 3MPG less per 30 mile drive believe it or not.. oh, and it feels flat as hell... Once you've remapped your 1.8T I think there are few cars that can match that kind of fun per £.