During the test flight of the flying saucer, a wire can clearly be seen attached to the aerial on top.
When the trumpet is playing at the beginning of the second year, the trumpeter's fingerings are all wrong. He is playing a bugle call, which does not require any use of the valves, but he is using the valves, so the call must be dubbed.
When they fly over Lincoln cathedral it's actually Liverpool's Anglican cathedral.
Flying time Lincoln to Blackpool in a Vickers Valetta would be less than 40 minutes, not several hours.
W/C Rudge (Milland) was supposed to have been a young "hot head" fighter pilot in WWII but Milland was 32 at the outbreak, very much borderline for combat pilot.
At the start of the film Flight Sergeant Harris ( Bernard Lee) welcomes the new recruits outside the accommodation block and is clearly their drill sergeant. However when cadet Winchester makes an unauthorised landing in his light aircraft causing the jet to overshoot, The Flt Sgt is the first on the scene. A drill sergeant like Harris would have no business going anywhere near the runway or airfield, let alone apprehend the culprit.