Sorry Tweeny, I've been away from home - ships very often have considerable history on sites - If you follow them up through a search engine you may very well find that former shipmates have associations whose members, between them, have an almost complete history of the ship. The only problem from your point of view is that the ships often outlast the sailors, so to speak, so many of the people you may contact may have served in the ship long after your grandfather transferred out of the crew.
I know a bit about the Bay class - my father-in-law was in two of them the Veryan Bay and the St Austell Bay. One tip when looking up the ships is to use the full name "HMS" whatever - otherwise you may get hits on the geographical feature after which they were named, rather than the ship itself.
One final point, HMS Collingwood was an initial training depot for "hostilities only" ratings. These were recruits whose period of service in the Navy was to be for the duration of the war, and no longer i.e. only for as long as hostilities lasted. This was in contrast to existing members of the Navy and those called back from Reserve status.
Best of luck in your search.