My Saab toolkit doesn't seem to have anything in it to remove the plastic caps that cover the wheel bolts. I didn't fancy levering a screwdriver against the nice alloy wheels. I've seen plastic 'tweezers' which the dealer denied all knowledge of and suggested needle nose pliers (hmm, that explains the scratch marks then .
Anyway, thinking laterally, I got hold of an 'IC removal tool' used for removing computer chips from their sockets. Works a treat I got mine from Maplins: Maplin IC Removal Tool but I'm sure there are plenty of other places to get them as well. Just thought I'd post this in case it was useful to anyone else in the future.