Continuity mistake: Throughout the first series Ben and Susan's bedroom had the window on the left of the screen and the bathroom on the right. In the second series onwards the bathroom and the window have mysteriously swapped around. Also the entire layout of the house changes dramaticly.
Plot hole: Janey is on the phone trying to win concert tickets and says, "She has to be caller number 5, rules of the contest are very strict." Susan then says something else and Janey says on the phone, "Dee I have to go, mum's going mad again." She evidently isn't on the phone to win tickets.