Another top tip. You can often 'negotiate' a good deal if you find a "wheel refurb" guy when he is working at the auction. The bigger sites usually have guys there almost permanently doing paint, wheels and screen chips and I have found them to be very approachable.
I parked a hire car in Manheim Colchester and had it keyed down the side for my trouble. Took me hours to get that scratch out with a mop!