Please could someone tell me what the following abbreviations stand for and where the unit was based. They are from the RAF service records of a former Halifax Bomb Aimer. All of the abbreviations are while he was under training in Canada. Thank you.

(6 Apr 1943 Embarked for Canada)

13 Apr 1943 31 DD or could be 3 IDD
15 May 1943 AWS or could be ANS
12 Aug 1943 1 "M" Depot
31 Oct 1943 5 SFTS or could be 55 FTS
11 Dec 1943 1 BGS
27 Mar 1943 4 AUS or could be AOS
9 May 1944 31 PD or could be 3 IPD
15 Jun 1944 H.E.

(16 Jun 1944 Embarked for UK)