get your choice of wheel sorted first as this could affect what size etc you want. we had a poll on this earlier so if you have a hunt back through the old posts you'll see a few opinions, but i think on a mk2 the general concensus is 15"s, for ease of use you probably want 7" wide and offset is around et 35 i think.
if you run 195/50/15 tyres you should have no worries with tyre clearance.
any one else got any thoughts?