Absolute twaddle !

Short answer: To cash in on the success of the title song. Other HH hits were featured as well.
Long answer: Herman's Hermits were on the MGM Records label in the US and most MGM Records stars appeared in at least one movie for MGM Studios-most were really low budget and pretty awful. A list would include "The Fastest Guitar Alive" (thanks for the correction) starring Roy Orbison, "A Time to Sing" with Hank Williams, Jr, the Connie Francis movies and the Hermits films. "Get Yourself A College Girl" and "When the Boys Meet the Girls" have a bunch of MGM Records stars in them. Elvis made a lot of movies at MGM. Instead of a straight salary for Elvis, his manager, The Colonel, negotiated deals with MGM that guaranteed that the less spent on the films the higher financial return direct to Elvis (and the Colonel). Veteran directors (hacks) that could "can" a movie in as short a time as possible were hired, existing sets & costumes were reused to keep costs as low as possible, etc. That's why the Elvis MGM movies are usually so bad. Since Elvis movies made a lot of money the studio decided to apply this formula to exploit their popular recording stars. Even bad movies can sell soundtrack albums if the music is popular-Elvis moved a lot of vinyl from his crappy movies-and that hasn't changed in modern Hollywood. MGM Studios was in constant turmoil from the early 60s onward with administrations changing and high profile projects being canceled left and right when new people assumed control of the studio. These low budget movies were so far under the radar the studio heads didn't interfere with them being made. They probably weren't even aware of them. Yet this dreck is what survives from the dying days of Metro-Goldwyn-Mayer.

I *LOVE* this film!!!! It is absolute twaddle but it's brilliant. It's so bad it's good. If you've ever seen Herman's Hermits in Hold On, you'll know this is actually the best film they made. Yes. Hold On was *that* bad!!!!

To be fair, I do think if it had been left to the Hermits and the younger cast members, the film might actually have ended up being worse than Hold On, but with great character actors like Stanley Holloway and Lance Percival it works a whole lot better.

Me, apparently. I'm watching right now on TCM and frankly, I can't look away. I'm 50 years old and suddenly, I'm a little boy again. Just hearing Peter Noone's accent (Cockney?) brings me back to the day my mom bought me my first transistor radio. Well worth a viewing, mate.