Continuity mistake: When Helen arrives home after being sacked (in the version where she doesn't catch Gerry in bed) he calls out to see if it's her. She replies "No, it's your bit of stuff. Wednesday, shag day, remember?" However it's been made clear from Helen's attempted replacement of the booze she took from work on Friday that it's actually a Monday.
Continuity mistake: When Helen catches her boyfriend in the act, we see very briefly that there is a gap between the bedside cabinet on which the radio cassette player is sitting and the wardrobe. This is more clear when her boyfriend switches off the music. Later when the other Helen comes home and her boyfriend leaps onto the bed to hide the earring we see they are much closer. Granted Helen now has two parallel lives but that can't explain the change.
Continuity mistake: When Gerry spots Helen at the post rowing activities he peers through the window. We can see 3 glasses from his side, one half pint glass partly hidden by the window frame and 2 pint glasses visible through the pane beside the one he is looking through. The shot from inside only shows two pint glasses in different positions.
Continuity mistake: There are two scenes when the different shots show blond Helen's hair first hanging in her face and then not in her face. One is in the diner with James drinking milkshakes and the second is when they bump into each other outside the restaurant when Helen has gone to track James down to find out why he hasn't called her. An even more glaring problem with the diner scene is that in one shot from behind her, Helen is pushing her hair behind her ear and the very next shot, which shows her full-face, her hair is still hanging down in her face.
Continuity mistake: Late in the film, there is a scene with James & Helen at night, in the rain on a bridge. The bridge is Albert Bridge. James is standing with his back to Cheyne Walk (north side of the Thames) talking to Helen. When she replies she is also standing with her back to Cheyne Walk.