Factual error: When Mainwaring is driving the van and Jones is in the back suffering from malaria, just after Pike shouts out that Jones has changed colour, if you look out the side window you can see a triangular road sign. These did not come into use until the 1960s.
Factual error: Captain Mainwaring is transferring money from his bank to another branch after it has been bombed. He has the money in a basket and is transporting it on a horse and cart when some of the money starts blowing out of the basket. Pike, Wilson, Walker, and Jones are riding bicycles behind him. They stop to pick up the money and just before Jones tells Pike to ride after Mainwaring to tell him about the money, you can see a silver car parked on the left hand grass verge in the direction Mainwaring is heading. This car was obviously made long after World War Two finished.