The King's rank insignia is incorrect. He is seen wearing the rank of Air Chief Marshal, one row of broad braid and three rows of medium braid. He actually held the honorary rank of Marshal of the RAF (One row of broad braid and four rows of medium braid). In addition the braid is white. It should be black with light blue insert.
At one point an officer with one row of medium braid on the cuff is addressed as 'Flight Lieutenant'. Flight Lieutenants wear two rows of medium braid. The officer should have been addressed as 'Flying Officer' who wear one row of braid.
The major's rank insignia (a crown on the epaulette) was far too small.
The ground scenes featuring German Messerschmitt Bf 109 fighters show the G-6 version (armored cockpit hood, rounded supercharger intake, rounded wing tips), which first flew in February 1943, 2½ years after the Battle of Britain. The proper version would've been the E-3 or E-4 (lighter cockpit hood, square supercharger intake, square wing tips).