wel i ordered my 20mm vw to merc adapters to fit my new wheels and have waited two bloody weeks as venom cant be honest with me and tell me where the hell they are

now been told they wont recive the 20mm's for another week or so and are sending me 25mm instead!
the wheels i have are 8.5j on the front and 9.5j on the back and im worrying that there going to exceed the arches by around 1 inch.
so what i really want to know is what is legal and whats illegal when it come to wheels exceeding the arches?

any help will be much appreciated. thanks, Ash