Mirrors, antennas, wipers, door handles, dummy spotlights, headlight lenses, red taillights, whitewall tires, chrome reversed wheels, spinner hubcaps...... Just to name a few...
The best stuff that I've used to remove any paint from plastic models is Scalecoat. You'll find it in well stocked hobby shops. Not sure if you'll find it in the UK. Just don't ever use it on any resin stuff because it will soften, warp and ruin the pieces.
I believe that the Masscar Model Club stopped putting on that show several years ago. I think that lack of involvement by a lot of the club's members had a lot to do with it. It used to be one of the premier model shows in the northeast and many good times were had both at the show and at the "get-togethers" at the Holiday Inn's pub Friday and Saturday nights.