It's a superb job isn't it?
Andy, I think the Spit is supposed to be black/white on the undersides. This scheme gave way to Sky by late June 1940, after the fall of France. A similar scheme, with a black port wing underside, was introduced on 27th November 1940, at the same time as the Sky spinner and tail band. Lock's Spit is depicted at the very opening stages of the BoB.