Chaps
You ask if there is a record of all Fleet Air Arm losses. The answer is yes - contained within "Fleet Air Arm Fixed-Wing Aircraft since 1946" by Ray Sturtivant, Mick Burrow and yours truly and published by Air-Britain (Historians) Ltd. Both Mick and I are currently finalising the rotary-wing companion volume to this (nine years in the making!) with a hoped-for publication towards the end of this year. This will have detailed individual histories for all helicopters owned/operated by the Royal Navy since 1943.
I've checked our Wessex histories and there is nothing showing for any incident on 25 October 1965. With regard to the 820 Sqn loss in the Straits of Malacca, only one is recorded - XS122 ('295/E') which suffered an engine failure, ditched but remained afloat (a rarity!) allowing it to be recovered aboard Eagle and returned to the UK for repair. Sadly it was written off in a later crash in 1972.
I'm still on the lookout for the loan of photographs that anyone might have in order to illustrate the book, so if anyone can help, please drop me a PM.
HTH
Lee