Continuity: There is genuine wartime footage of Spitfires of the the right type for the period, but other scenes have later (maybe even postwar) versions flying about.

Continuity: Near the end of the film much is made of Alec Guinness' self sacrifice in breaking radio silence to report the position of a German-Italian convoy. In due course he is shot down by German fighters, only the convoy had already sighted him and were shooting at him, so his breaking radio silence surely wasn't going to make his position any worse. In addition his stripped down, souped up photo-recon Spitfire was theoretically able to outrun any enemy fighter. If he was shot down it was not likely to be because he used his radio.