Goofs

The colour of the foil tops on the milk bottles changes colour between shots. They are silver when they're outside on the doorsteps with the robins picking at them and when the housekeeper picks them up to bring them in. When she puts them on the breakfast table inside in the next shot, they are golden.

Towards the end of the film Kitten pretends to be doing a survey for British Telecom. British Telecom didn't come into existence until 1981.

In the scene where Patrick is asking the construction workers in London about the whereabouts of his mother, you can see a few modern-day cars pass by in the background, under the bridge.

Whilst the film is set in the late 1960s, early 1970s, the scene at the train station shows trains of the 21st century.

A copy of the board game Scotland Yard by Ravensburger is in the stack of games inside of Billy's mother's caravan (mobile home). That game was originally produced in 1983.

Although The Wombles would have been at the height of their popularity during the film's mid-70s setting, the appearances of the featured Wombles are based on the designs from their late-90s revival, in particular Wellington. Also, Alderney is shown - although included in the books, she didn't make her screen debut until the 90s series.