<<the London Control was carried out by the former RAF Sopley site. >>
Control was exercised by London Airways from the Southern ATC Centre at Heathrow and Sopley was an outstation. In those days, procedural control was in the hands of the controllers at SATCC who could call upon the radar controllers at Sopley when needed. (Maybe some older hands could expand on this please?)
I'm not sure when the College of ATC started but when I did my course in 1971 the College used the Hurn Airport radar and the only flying associated with the College was by the Ministry of Aviation Doves used for ATC radar training.
HTH