A.LDG.SEA is a badly written abbreviation of Acting Leading Seaman which should be refer to as A/LS in official terms but was often seen in WWII RN ships crew listing.

TY is for Temporary, but the RN didn't give out temporary promotions to Junior Ranks, and wartime ratings were refer to as Hostilities Only (HO)during the earlier part of WWII. I have seen the TY abbreviation in some WWII crew listings but have no idea what they refer to.

For Sailors, the ranks were Seaman, Ordinary Seaman (ORD), Able Seaman (AB), Leading Seaman(LS), Petty officer (PO) Chief Petty Officer (CPO) and Warrant Officer (WO), anybody below a AB were normally refer to as a seaman and abbreviations were rarely used to describe them.

Its only in novels that you see things like Able Bodied Leading Seaman describing a rank.