I would suggest you approach the Roayl Engineers Museum and Archives. Whatever else your father did he did not go "on the Atlantic convoys to Murmansk". Atlantic convoys went across the Atlantic, west of the British Isles, Murmansk convoys went through the North Sea into the Barents Sea east of the British Isles, to Murmansk which is the northernmost Russian Oblast. He could have gone in both directions but not at the same time.