Continuity mistake: Approximately 9 minutes into the film there is a scene with 'Koop' talking to a customer in the record shop. The camera cuts back and forth between views from either side of the counter. Look carefully at the turntable on the counter and you will see that even while the turntable is not switched on, the deck is in different positions between camera cuts. This is easiest to notice by looking at the angle of the word 'deconstruction' on the blue slipmat. There is even one cut where the turntable's arm is sitting in the middle of the empty slipmat, and in the next cut (and the previous cut), it's on the armrest where it belongs.
Deliberate mistake: In the short scene where Jip is driving his car and talking to the older man in the passenger seat, the car is driving down Marlborough Road. The camera cuts between Jip and the man several times, one shot of Jip shows a building where some tennis courts are, another shows Marlborough Road School and the last one is going past some houses. In the last one he should be going past a shop called Bedybuys.