Wendy, no luck I am afraid, as Hugh has come back and informed me that crew Agreements where not completed for Royal Navy Ships, but has pointed out a number of files at the national archive. Only thing is that you would need to go to Kew to view them.
As far as I am aware, there where only Survivors from the convoy that Anking was part of, and they were picked up by a Dutch Sumbarine, and taken to Columbo, Ceylon.
I think that it is more likely that your Uncle left was on board one of the many ships that left Jakarta on the 26th / 27th Feb, but not as a member of the crew hence why he is listed under HMS Sultan
P