Fifty Ships - S2-E1
Factual error: In the scene when Foyle meets the Home Guard colonel, Letwin, the colonel, has his Sam Browne belt slung over his left shoulder which is totally wrong, especially for an officer risen to field rank. Apart from being intended to provide support for the officer's sword (even if not worn and even if his service revolver is likely to induce sagging), the belt slung over the left shoulder will obscure medal ribbons. Horror of horrors.
Fifty Ships - S2-E1
Factual error: One of the wall pictures in the departure hut in the penultimate scene appears to show passengers boarding a Comet jet airliner, introduced in the early 50s.
Answer: They are using the accepted names of the bombs. During World War 2 the Germans used the metric system and produced bombs ranging from 50kg to 2500kg. Referring to the weight of the bombs in pounds (or fractions of tons) risked confusing the situation and would require someone to understand how to convert from imperial measures to metric, not an easy thing to do when under stress.