Wasn't it Elmbank Foundry that was bombed out interrupting the bracket supply? But not sure if that was their operation in London or Glasgow? Can't find any reference in a few minutes googling as to when that occurred either.
Considering Rose Bros. was so busy working on turrets etc. for Bomber Command, perhaps they gave it up at some point, or was it the case that both they and Dalgleish continued making brackets to the end? If so, perhaps a wise division of effort to avoid another such interruption?
Have never heard any suggestion that H&H dragged out the early rifles at the end of the war to keep the contract going - not sure where that idea originated!