No problem, an easy mistake to make. I also put the question to Edgar Brooks, who had already been of considerable assistance to me on yet another issue (three- vs. four-spoke hubs). Here's his answer:
Metal elevators were introduced, as mod 1598, for the 21 only (initially,) from 15-1-47, and could, presumably, have been retrofitted to some post-war "fliers," as well. Wartime Spitfires didn't have them, though all Seafires did, so, eventually, they would have been easy to get hold of
Good enough for me!
Jean