In Devon in June 1944, sunset would be after 10 p.m. (Double Summer Time), and, indeed, when the clock strikes 9 and Bridie suddenly ends her date with David, they are seen moving against a daytime sky. Yet in the prisoner scene occurring simultaneously, it's fully dark.
Miller's body is wheeled through town with his hat covering his face, so townspeople assume it is "Grandpa". When Bridie returns to the hotel, she sees Miller's hat still in the room and must hurriedly dispose of it so that she is not in any way linked to him or his sudden disappearance.
When David takes Bridie for a walk on their first date, she is wearing a plain dress in the initial wide shot but a striped dress in the closeups.
Bridie was told that Woodbridge was in the West Country; leaving there by train, when it stops at a main station, the announcer says that it's calling at Pontypool Road, Hereford, Shrewsbury, Crewe and Manchester. This would indicate that the announcement was made at Newport (South Wales) station, so it's confusing how she got there from the West Country, plus the only Woodbridge with a station is in Suffolk.
In the station buffet at Crewe, Bridie sees a newspaper headline stating 'Suspected German spy shot'. Later in a Liverpool hotel room, she takes a newspaper out of her handbag and unfolds it to a back inside page where the headline about the spy is, not on the front page as would be expected. Later, she picks it up again, but it's now folded to the front page which shows it to be The Northern Echo. This paper is based in Darlington and only circulates in that area. While a copy might have been left on a train, those only go North and South, not to the West Country. The Echo at that at that time was the same format as the Telegraph, so it would have been impossible to fold it up to fit in a handbag.
The same truck with the same numbers on the back right door is used to deliver two separate prisoners to the train station, one after the other.
Bridie is never seen to smoke throughout the film, but when the wounded J. Miller asks for a cigarette, she takes a cigarette case out of her handbag.