On Mk2's with standard arches and suspension we have used 9" rims with 8.5" tyres.. all depends on the offset of the wheels.
but if you want it to handle better, whatever wheel you fit make sure the rubber is the same size or slightly smaller , and dont take no notice of the numbers on the tyre sidewall unless its a race tyre, as standard road rubber includes the tread that goes down the sidewall . Go out side with a rule and measure across a standard road tyre on a car, measure the part that is clean and worn, then check the number on the tyre sidwall.

On a 7" rim i would be looking at 185 max for spirited road driving and and 175 for trackdays... but like i said thats measured width, not numbers

Manufacturers quote tyres to comply with NVH ... and we're not bothered about feeling road undulations and hearing noise ...Are we?