Hi Douglas,
If you are going to TNA Kew, you can also obtain his service record called a form CRS 10 and in the absence of his discharge book and indeed the crew list will be acceptable as evidence along with the movement card.
The form CRS 10 is held at Kew in piece
BT 382/1933
You are most likely also aware that he also served during WW1 and in 1914 was aboard ARANMORE as 2nd Engineer. He also served in TUSKAR, ARANMORE, SANDA and PLADDA during 1915 in the home trade as Chief and 2nd Engineer. He has a WW1 and a WW2 medal file.
He has a CR 10 card with photo id taken circa 1918/19 and serving on PLADDA during this period. If you need the card let me know?
Regards
Hugh