ive just fitted a new set of wheels on my rb5, they fit ok but there is hardly any clearance on the 4 pot brake caliper on the front. took it to a local garage where they said it was safe enough but i should think about fitting spacers.
if i do, is it going to bugger up the cars handling or anything?

A 3mm spacer won't do anything you'll feel and is fine. Only when you get over 5mm what you should have a full kit.

But if they clear what are you worried about, I've had some that have only just cleared and they've been fine.