Yeh its surprising just how much a difference the little mods make to how the car looks at performs.
my bumper was like yours but I did cut the valance personally I regret doing it now as although it looks alright it can be a pain if the tip I welded on moves and rattles against the bumper I would recommend a scorpian cat back system from ebay for the mk4 golf it has the hidden tips so will look standard but sound good aswell then get the valances colour coded as it gives the car a wider looking stance when lowered and alloys fitted.
yeh defo go for 17's no bigger as also if you go bigger the steering rack wont take 18's as its different to the cupra's so will rub on the arches with 18's.
I got the grill from david at sere motors he is a very helpful bloke heres a link to his section of the forum on here just ask him for the upper outer and inner honeycomb cupra grills.
http://www.seatcupra.net/forums/forumdisplay.php?f=249
there was a fair amount of work invloved in making the grill fit as it originally comes in a 5 foot box with a plastic bumperbar moulded to it but after a bit of cutting I had mine fitted perfectly.
where abouts are you from matey if your local can always give you a hand with a few mods
cheers well im want the exhaust to come out the back so im gonna just get a new valence now i just need to save 570 for the rims i want,
btw did you buy a new suspension kit or just new springs?
I'm on the Isle of man haha my local garage have a pretty extortionate price list, so me and my uncle would probs do the mods