42C
Dsrsia, at first I misread your post as you said that your Father joined in Sept 41, then I realised it was 42C. My uncle (and REGLE Reg Levy my dearly departed friend) started in June 41 with 42A, my uncle was "washed out" and re-appeared in BFTS 1 got his wings and went "spitfireing".
What interests me is that you have found documents at Kew? I searched and failed. Could you possibly advise me of their location codes?
Andy