It's a shit trailer. And the music isn't the same as used in the film.

I saw the film around 1972 when I was an impressionable 16 year-old (and was duly impressed by it). It's better than the trailer suggests and still watchable as a sad, funny, film that subverts much of the swinging consumerist ideas and imagery of 60s England (London in particular). A period piece, though.

Edit: just seen a 2011 Grauniad article about it.