Tom Brooke-Smith
The book on ETPS "Learn to Test, Test to Learn" has following.
Despite the interruptions, No 6 Course (1947) managed successfully to complete by the end of the year.
The one civilian test pilot on the Course was Tom Brooke-Smith, who had come from Short's at Rochester where he had been busy testing the flying-boats. He went back there as Chief Test Pilot, going on for years and testing the VTO testbeds built by Short as research aircraft in the sixties. From there he went to Flight Refuelling Ltd, at Tarrant Rushton.
Unable to find any of the others in my listing of ETPS graduates.