That's why I thought the TX referred to a transfer rather than a Terminal date.So going on what you have previously posted and the snippets of the SC that you have shown us I can categorically state that he was transferred from whatever rate and branch he was in during feb 45 and became a patrolman.
He would have to relinquish whatever rate he was to join the patrol service. He undertook his training at HMS Drake and was then promoted to acting leading patrolman in aug 45 and it looks to me as he served until he left the service in july 46.
So that would have been his demob date.
If you can scan a more in depth copy of his SC we can probably tell you some more.