First off, if you're looking for movie with The Small Faces, this ain't it. Even though The Small Faces are touted on the front cover, they have hardly any presence in the film. They're shown a couple of times getting out of a van, once for a photo shoot, and when playing at the final concert, they get about a minute of screen time with the rest of their performances being heard in the background.
The plot: The Small Faces manager is an ex-con who gets blackmailed into smuggling diamonds to the Radio London ship (as seen in the fictionalized "Pirate Radio" movie"). The best part of this is the blackmailer looks like Peter Sellers as Inspector Clouseau.