Agree about the Valetta, though not certain whence they came. Logically it would have been 48 Squadron based at Changi before it re-equipped with Hastings in June 1957 (from Wiki) :-
https://en.wikipedia.org/wiki/No._48_Squadron_RAF
Certainly crews were seconded to Katunayake (Negombo) from Singapore to fly the Gan Shuttle (9 months detachment mentioned here) :-
RAF Gan Remembered - This & That
though the picture was taken after the re-equipment of 48 Squadron, so possibly it had a mixed fleet still at the time? Others of course will know better than I (they always do!).