There’s been a lot of anticipation for this film by John Cameron Mitchell, who brought us the entertaining Hedwig and the Angry Inch and the sombre and moving Rabbit Hole. Mitchell returns to the punk territory of the former, but unfortunately with less success.

We’re in Croydon in 1977. Punk is at its height and Queen Elizabeth II is celebrating her silver jubilee. This choice of 1977 gives the director plenty of Union Jacks and street parties to set against the iconic Sex Pistols song and record cover, which he uses consistently throughout the film. Our hero is Enn (Alex Sharp): he’s being raised by his single mum, his jazz musician dad having abandoned the family ship years earlier. With his two best mates, the chubby and cerebral John (Ethan Lawrence) and the Billy Idol lookalike Vic (Abraham Lewis), the three schoolboys have embraced punk. It’s unclear what has brought the three together, for the good-looking Vic doesn’t quite fit with his two less cool companions.

However, if we can accept Vic as part of the trio, what we can’t accept is Nicole Kidman as Boadicea, the queen of the Croydon punks and a terrible piece of miscasting. Boadicea runs a club and talks of her past relationships with the likes of Sid Vicious and Vivienne Westwood. Those who grew up in the 1970s would find it hard to remember any middle-aged punks around at the time. As Boadicea, Kidman has been given a wig that makes her look like David Bowie in Labyrinth and her accent lurches from broad east estuary to straight-up Australian.

After hearing a band at Boadicea’s literally underground club, the boys set off in search of the after party (though just for the record, most little local bands didn’t have ‘after parties’). They hear music and come across a large house. However, this is not a punk party, but the home of aliens. The film has been pitched as a punks versus aliens movie, but when the punks are not very punk and the aliens look like acrobats from Cirque du Soleil, that pitch is pretty misleading. There are various groups of aliens, handily wearing different coloured lurex outfits. One group contains Zan (Elle Fanning) and she is questioning the group’s philosophy, which is pretty much to eat humans in order to survive. When she meets Enn, a charming and often extremely funny romance ensues. Fanning is excellent as Zan, all wide eyes and inappropriateness as she strives to fit in with the humans, and she and the talented Sharp make a great pair, providing the film with most of its laughs.

As with most sci-fi, this film deals with contemporary issues: namely, don’t treat your planet badly and learn to live harmoniously. Yet there is little sci-fi here, probably due to budget limitations. The balls of light swirling in the darkness are like cheap reminders of the globes in Inside Out and there are a few too many penetration jokes, along with a myriad of cheap costumes. Another issue is linguistic, for although we are in 1977 the language is much more contemporary, which grates.

For all this, the film is a fairly likeable one. Fanning and Sharp are the high points, and Ruth Wilson makes an entertaining appearance as a dominatrix/alien, and looks like she had fun doing so. (Matt Lucas is also present, but has a pretty anonymous role.) But will the film teach you how to talk to girls at parties? No. Will it inform you about punk? Absolutely not. Will it satisfy your sci-fi needs? Nope. Nevertheless, it is a sweet and harmless film that will probably find an audience more generous and forgiving than this critic.