In the final scene in Peter's bedroom, the tape recorder appears to be running backwards (playing from right to left). But in the next closeup shot as the tape runs out, the machine is running forwards with the left hand spool running out at the end of the tape.
When Peter leads Brenda/'Wendy' into her room for the first time, a crew member is clearly visible, crouching down from the doorway.
Brenda lives with her mother in Liverpool and tells her she is going to London, however the opening establishing shots of "Liverpool" were actually filmed in Battersea, London.