Other mistake: Just after the Royal Navy destroyer has sailed through and depth charged the area where the British survivors are, there is a shot of the churned up sea with sombre music playing, and the seagulls are flying backwards.
Other mistake: When the Geneva man is inspecting the barracks, he is told that "each barrack holds seventy-five men." At best count, there's only thirty to thirty-five at any time, and the correct number of bunks.