ADU RAF Chessington

I am currently researching a Sergeant MU A/G who was awarded the DFM in December 1943 and was shown in the Squadron ORB’s as posted to ADU in Chessington in February 1944, along with his Sergeant R/G.
My understanding is that this was a posting for aircrew with LMF. Could it be that two gunners had this at the same time and would therefore be posted out? Would the MU A/G forfeit his DFM?
Many thanks for any thoughts or confirmation.