I noticed one reviewer compared this movie to the later American film "Bye, Bye Birdie"...and that is a pretty astute observation. Both films have a lot of similarities, though "Birdie" is much more of a musical, though there's plenty of singing and teenage hi-jinx in both.
When the film begins, the American crooner Bobby Denver (not to be confused with the "Gilligan's Island" actor) arrives in Britain...and the women there are losing their minds for him! Shortly after his arrival and the mobs of women attack him, he is tricked into going to Wimbledon (just outside London) to stay with the Bentley family. As for the Bentley's, the father is the world's biggest square, his wife is sadly neglected and their three daughters are screwy! Now, you add Denver to the household and chaos naturally ensues. But something else happens...and that you'll need to see for yourself.
According to imdb, Bobby Denver is a character inspired by American singer Johnnie Ray. While he's pretty much forgotten today (partly because he went deaf while still quite young), apparently when he visited the UK and Australia, it was like Beatle-mania and Elvis--with screaming women following him everywhere!
So is it any good? Well, yes...but I should point out that the film is NOT subtle in any way! In other words, the humor is pretty broad and low-brow. As for me, I didn't mind this and a few of the jokes were cute--such as Denver's propensity to cry and make people cry as well as how the women of the Bentley household got over their infatuation with Bobby. I also enjoyed seeing Diana Dors in the movie. There really was no reason for her to be in the film, but she was nice to look at here. But remember....the film is certainly not subtle in the least and may annoy you with its characters who seem, much of the time, like caricatures. I can see why some reviewers hated it...but I didn't mind the silliness.