Oh yay something I can talk about.
To elaborate, most of the ww2 leaders still left in England are collaborators yes, by virtue of the fact that most of the others are exiled (Churchill), dead (Mountbatten, Pollit) or at the least nominally out of politics contrary to the government(Wingate, Auchinleck, Jellicoe). The Collaborators by this point have destroyed or surpressed almost all the original resistance movements with the exception of Stirling's mad band. (who isn't quite Karby levels of "revenge" but comes closer than you'd think.
Thus by default, with the exception of the higher echelons HMMLR as a movement has been forced to draw from men and women who were too insignificant or low ranking to be caught in the German (and later, Collab) crackdowns. Wilson to use the easy example, was an insignificant member of the government whose highest achievement was being an economics lecturer at Cambridge before he joined the Labour Underground.
And besides, Arthur Harris is working for HMMLR and he's perfectly sane!