I'm sure if you look hard, you'll find a nice example for that amount, i paid way less for that and got an immaculate car, although the milage was slightly above average. Try the usual places e.g pistonheads, autotrader and the sales section here and im sure something will catch your eye. Personally i dont consider mileage as the most important factor, moreover full history, the way it has been maintained and appearence.
There is a shed load of info about buying the gti 1.8t on this forum so try a few searches and im sure the rest of the mk4 lads will be along soon to give you even more info.
your making the right choice 1.8 gti t + re-map = happiness
