I get this all the time!!! I think there must be something inside the filling hole on the GTI that stops you being able fill it up easily!! 
T88OMM where have you beeeeen!!!!!!!
Been bloody busy past couple of months, work and the missus are takin over!!! Unfortunately the car has been the victim in all this! No modifications whatsoever, I really cant get a TTS off my mind at the minute so I think im holding out spending cash on mods and putting away for one!! Just got back from my road trip to Portugal and it was an absolute blast, some of the roads were incredible, namely the Stelvio Pass, WOW!! I should be around a lot more now, sorry to go off topic!