The soaps, towels etc wouldn't be marked "HMS" (Her Majesty's Ship) as this is merely a title for a ship and would always be followed by a name. Rather, they might be marked "RN" for "Royal Navy."
The large twin barreled gun on the deck had no capability to raise or lower the barrels for aiming as there was no vertical slot to allow them to be moved up and down. They were "welded" solidly onto the turret.