I take it your mk2 already has 18s right?
How do u get on with driving on the UKs roads with the 40 profile tyre you already have?
I have 18s as standard and find myself being extra cautious on todays roads what with all the potholes,cracks and speedbumps (i actually now avoid roads that i know have speedbumps)...i guess what im getting at is that the ride is firm now with 40 profile tyres (what are 19s 35?).
If your happy with 18s but must choose a diff set of rims then stick with 18s but if you want the looks then 19 it shall be,but make sure your happy before purchasing as the ride may or may not be just as hard if not harder....hmmmm toughie