Revealing mistake: When Stan reverses the bus into Blakey's minivan, crushing it, the van that is crushed is not the same one that is used earlier in the film as it is tatty and has a different grille. Also, the bus parked behind which the van is crushed against is so obviously fitted with an extra panel, to prevent body damage when the van is pushed into it.
Continuity mistake: When the fire starts in the bus depot, the manager tells Stan to reverse the bus away from it, and ends up crushing Blakey's minivan. The van changes from a Morris model to an Austin model, just before it is crushed.
Visible crew/equipment: After Arthur's bike has crashed into the road workers hut, it goes along the road with the hut on top of the bike. If you look through the hut window you can see some crew members holding the hut up.
Continuity mistake: At the darts match, Arthur's clippie Nora is wearing white boots. But when she's fighting with Olive, her boots have changed to black. Then after the fight they are white again.
Revealing mistake: At the beginning, when the car drives through the puddle splashing Blakey, the water barely reaches his knees and it's obvious that the water that hits his face is thrown out of a bucket.
Other mistake: When Stan is towing Arthur's motorbike and sidecar behind the bus the tow rope was attached to the handle bars, when the handle bars come off, the bike naturally breaks away from the bus and rolls off on its own, but it is going back the way it was when it was being towed. The bike couldn't have turned 180 degrees with no handle bars to steer it.