I also thought that the Heathrow zone should have been class D.
I seem to recall Gatwick's zone is..and there dosen't seem to be much of an issue there.
My biggest moan was police ops over Twickenham on a gin clear 100 Kms vis no clouds CAVOK day being considered "not separated" from arrivals...when traffic info suffices perfectly to all concerned. It works everywhere else!?
Either that or close all the other airfields around London..Battersea, White Waltham, Elstree etc etc. That would then rid you of most of the originating traffic that causes these problems...and all would be well......maybe?