Continuity mistake: When the police are interviewing people about Mr Volker's death, the girls are talking to the lawnmower man, who turns the ignition on and releases the brake, but in the next shot he reaches down to release the brake, despite having already done it.
Continuity mistake: The first time the girls park outside Helena's place, they park further away from Helena's red door, as does the motorcycle in front of them - both of them park outside a blue door. But when Helena opens her red door, the Rover and motorcycle are right outside.
Plot hole: The girls refer to Holly's owner as Mr Volker, even though they now know her owner is Mr Allbright. For plot reasons, they have to say to Sherry that Mr Volker is Holly's owner, because now she knows she's killed the wrong man, and she'll have to kill again.