Wheel opinions, GTC01

[s4mmie]

I wouldn't think there would be a problem. They're only really there to serve as protection from crud, not forming any structural part of the car. You're not cutting any metal, it doesn't affect any aspect of how the car behaves. You'd have to check the current NCOP, I'm used to old school cars that are all metal. Plastic bits might be a bit of a grey area...

<EDIT> Just had a quick once over the NCOPs and can't find anything about it. If there was anything to worry about you'd find it in there. I would say it would fall under modifications that don't require certification, like bonnet scoops, tubbed arches, etc. ie legal

[noone]

You don't want wet crap getting places you can't clean, sure to rust sooner or later.
You could modify them, there are only a few key places they interfere. On 35's my rim has less than 10mm clearance to the strut, so you will always have the poke vs strut width and offset limitations.

Unless you get Polo S2000 arches. Do it.