Continuity mistake: In the scene when his old school teacher comes in to pay for petrol, he hands Alan his credit card. The two of them chat and the teacher proceeds to leave, claiming that if the pupils need someone to talk to them about working in a petrol station, he'll be onto Alan. Alan dismisses that he works in a petrol station, and the teacher says "But I've just paid you for petrol and a packet of Minstrels." Actually he didn't, as Alan never swiped the card and the teacher left with free petrol and chocolate.
Continuity mistake: After the cow is dropped on Alan's boat, there is a quick scramble of shots. One of the shots shows the farmers who just dropped the cow. However, this camera shot shows them (and the bridge) as being a lot further away than they actually could be having dropped the cow only a few seconds earlier, especially given that the boat is moving slowly and appears to stop when the cow is dropped.
Continuity mistake: During the meeting with Pete, Michael comes in and lowers the torches attached to the bicycle wheel. He lowers the wheel, and then uses one hand to turn the torches on and the other to hold the rope to stop the wheel from falling to the ground. The shot cuts back to him and he is now using both hands to turn the torches on and the rope has already been tied off in the background. The shot cuts away and then back to him and the rope is back in his hand and he walks across to tie it off.