Aviate1138: I'm aware of the assembly of Wimpeys at Smith's Lawn, but where did construction of the parts take place? Years ago I read a book called 'Beneath the City Streets' which mentioned an underground aircraft factory under Wentworth Golf Course which as you're probably aware, isn't too far from Smith's Lawn, so could it have been there?
(Thinks - purely imaginary - if you could find the entrance to this factory, would you find tooling/jigs/parts still there?)