Hi and welcome to the forum. Its good to have you here. gtigrl also has a silver GTI Polo. The wheels do look naff on them, for sure! I suggest that to find the offset you could check out the spare as at least you do get 5 of the wheels and no spacesaver.5x100 stud pattern and I think they might be 40 ET? They are the same as on the Mk4 Golfs and Boras. I suggest you run higher tyre pressures to what they recommend too.
Hey, good luck today with picking up your new Polo, 1st VW? And once again, welcome. I hope you have happy motoring! Cheers, Andrew