When Pauline is standing in front of her newly destroyed house, in the close up shots her hair is flat, but in the distant shots it's noticeably more full.
The ammo-round would not have fired normally while just being gripped in the jaws of a vise; without the round's being contained in a gun-chamber, the powder would have exploded the brass casing.
At the end of summer (as Bill is about to go back to school), the family is listening to Churchill's "end of the beginning" speech. The speech was given on 10 November 1942, not during the summertime.
Dawn would have needed to lie down to give birth to the baby; she could not just have it standing up.
The string quartet of Grace, Faith, Hope, and Charity is clearly not actually playing the piece of classical music near the end of the film. Also, the Mozart serenade in G K.525 (Eine kleine Nachtmusik, or "A Little Night Music") that they are supposedly playing is scored for five instruments, not four.
When Bill is being chased, the dog is running next to him in the last couple of shots.
The man is incorrect when he tells the boy that they (the Nazis) will be bombing France with Big Bertha which has a range of 25 miles. Big Bertha was a nickname given to a gun the Germans constructed in the first World War. It was made by welding 3 gun barrels together which gave it a range of 75 miles.
At 1.14 into the film, when Bill leans on a supposed brick fence to pick up Dawn's ring, it gives and then comes back upright.
The headmaster implores "God save us from the Messershmitts and the Fokkers" in the school assembly prayers. The Luftwaffe didn't have an operational Fokke-Wulfe combat aircraft during 1940, apart from a limited number of Condors that were used to attack shipping in the Atlantic.
The Fw190 was introduced in 1941, as the be109 was being phased out.
Along with the be109, the Junkers 87 Stuka (dive bomber) was the most notorious Nazi aircraft of the Batttle of Britain period.
Medium bomber manufacturers of the aircraft used to bomb London were Junkers Dornier and Heinkel.