Ah, that fits in just right with his service record then. On the last image you posted there's a stamp that starts "A & S Gp" with 25C written after it. As I understand it, as the war began to draw towards a close planning began for an orderly demob of the millions in service. Each was allocated to an Age & Service group, based on how old you were and how long ago you were called up. The lower the group number, the quicker you were eligible for demob. My grandad's group, written on his records, was '27C' and he finally got demobbed in early April 1946. I don't know what the C refers to. Your grandad's was 25C and it looks like he was released a few months earlier.