Cheers chaps, here's some photos, the best of a bad lot!
I got nearly all the details parts off, but didn't fancy trying to peel off and re-attach the Ferrari badge on the boot which appears to be a raised chrome decal, about 11mm long.
I decided to get the colour behind the letters by airbrushing a light coat of paint on, then wiping off with a soft cloth, til the colour was dark enough. This worked, so I then masked off the badge and sprayed the rest of the boot. Unfortunately the masking lifted the "i" off the end of the badge, which then broke and disappeared.
I have painted it back in by hand using a fine brush and Humbrol silver Enamel. It isn't bad, but is noticeably different.
Replacing the boot lid would be the best solution, but a nice lady from Mattel called me back after I emailed them to tell me they don't have any spares for this car...
Any ideas?

... other than spending £50 on a new model!
While I'm on, does anyone have any tips on how to gat a high gloss with Tamiya acrylics? Can it be polished? My main hobby is airbrushing crash helmets, but the lacquering is done by someone else in 2 Pack, so I don't normally worry about finish!