I've now received my copy of "Naval Fighter Pilot: Lt. Cdr. R. J. Cork DSO, DSC, RN", by A.H. Wren. On page 123 Wren has a quote from the 880 NAS record book entry for 20 February '42 which reads "One of the RAF Hurricanes Mk II which was left U/S had been converted into a Sea Hurricane was air tested by Lt Cdr Judd. This aircraft was taken over by the Squadron." Indomitable did not arrive back in Aden until 22 February, so it's quite clear that this aircraft was converted to a Sea Hurricane on board the ship. This was presumably BD771 but Wren does not say so.
Wren also quotes the Squadron Record Book as saying that 60 RAF Hurricanes were flown off on 6 and 7 March '42: "880 Squadron pilots acted as guides when the 60 aircraft were flown off in four batches at 0740, 1140 [6 March] and two further batches the following day. Lieut Cork (O/C B Flight) led largest group and gave them a guided tour of the island."