I had a little time last night so I decided to check out the headset in detail. Amazingly, the races have no blemishes and look as though they came right from the factory. I pulled the bearings apart, soaked them in some degreaser and they came out clean and are in really good shape too. A fresh coat of grease for the balls and cage, sealed them back up and they're ready to go. I'm waiting for a nicer day to clean the frame really well and once that'd done I'll start in on the re-build.