The damaged Vauxhall Chevette has registration plates with a different spacing, indicating it was probably a different vehicle. (The original undamaged car reappears later in the film).
At 28 minutes, no rear view mirror in Bob Ferris's Vauxhall Chevette, but it has been re-attached when the car is shown parked up at the caravan site. The mirror disappears and re-appears several times during the hitch hiker pick up section.
The time between Bob being knocked over in the library and him dropping the brick on Thelma's foot was not long enough for him to get back up.
When Bob and Terry do a u-turn across the road to catch up with the girls, the cars on the other side of the road change between shots. There are no oncoming cars at all in the shot from inside the car as they make the u-turn.
Thelma opens the door to Terry's flat by pulling the key through the letterbox to let herself in. As she does so, the shot changes to an interior one, where the key is still hanging on the inside with no time for her to have replaced it.
The Fat Ox pub is being demolished as drinks are served. There is no way that they would pull down the pub whilst it was still open and serving drinks.
Neither Bob nor Thelma show any signs of breathless after having had to walk up to Terry's flat which appears to be near enough on the tenth floor of the apartment block.
Bob would have been unable to drive safely towing a caravan because the car has no wing mirrors.
Bob's car in the final scenes has wing mirrors, though they were absent when towing the caravan earlier in the film.
The Vauxhall Chevette was never sold with wing mirrors. They had door mirrors, and in many scenes the two screw holes for the missing door mirrors can be seen on the doors. For some reason the film company removed the door mirrors and stuck on prop wing mirrors.
When Bob and Terry pull up in front of the Ivanhoe guest house there is a reflection of the camera crew on their car.
The Boys take the girls to a holiday caravan camp at Whitley Bay, just North of Newcastle but go through the village of Rothbury which is some 40 miles further North.
Bob is driving a Vauxhall Chevette, a small economy car that sat below the Vauxhall Viva in the market. He must have gone down in the world because in the TV series he drove a Viva.