Factual error: At the beginning of the film, just after the credits, there is a definition of the word 'army'. It is claimed to be from the 'Encyclopaedia Brittanica', an obvious spelling error - "Brittanica" should have one T and 2 N's.
Continuity mistake: At the end of the film, Lieutenant Perry orders two men to take the Vickers .303 machine gun into the Frenchmans cafe. It cuts to a close up of the gun, which shows it's a WW2 era Vickers with a smooth water jacket. The men run and pick it up, and carry it into the cafe. When the scene cuts to inside the cafe, the Vickers has suddenly changed to a WW1 era Vickers with a fluted water jacket, which it stays as for the rest of the film.