Revealing mistake: The councillors put red paint in Beaumont's hat and put it on his head, squirting paint out through the top, but when they are pouring the paint into his hat you can see it already has a hole in it to let the paint out, and the way they are holding the hat shows them covering up the hole to stop the paint coming out before it is put on Beaumont's head.
Continuity mistake: When the gang are trying to push Gerald's car which is stuck in the mud, the wheel is spinning in the mud but the wheel arch is clean. As soon as the wheel stops spinning the wheel arch is covered in mud, and when the car drives off by itself after it has been left it in gear, the wheel arch is clean again.
Other mistake: Whenever you see the gates to the yard during the show they are painted green and have a "Wright and Boston scrap metal merchants" sign written on them. But right at the front of the opening titles of every episode, the gates are plain green with no sign-writing on them.