Hi Migs
The early Night, White and Aluminum scheme that you refer to was used only from Feb to May 1940 and the Aluminum was painted, not bare metal. Mostly they were Night and White, split right down the center with even the tailwheel being Night on the port and White on the starboard and this also included the wheel wells, oleos, oleo fairings, and main wheels.
When you say the wheel wells would be clean, don't forget that they were operating off grass aerodromes and the mains would spray any mud etc right up into the wheel wells. I usually give mine a wash of Grimy Black mixed with some Dark Brown and also do the oleos and the oleo fairings and wheels.
BTW, which Osprey book are you refering to? If it is the Osprey Modelling Manual, get rid of it. I wrote seven pages of corrections for mistakes made in that book and sent them to Osprey. They put a stop to publishing on it. It is probably the worst book that I have ever seen for Spitfire reference. The author hasn't a clue about what he is talking about and is not much better at building a model.
Cheers
Bob S.