I don't know if Britain ever really achieved that much glamour. We had post-war austerity rather than post-war prosperity, and our cultural products of the time include some pretty dour kitchen-sink dramas of the A Kind of Loving variety. (This kind of film seems disillusioned with the sixties before they've even really begun. )
Most musicals are informed by very rigid archetypes. If you get a very sophisticated mind writing them, you sense something else, but it's a folk-art form, really, at its best. At different times I've tried to push against it as much as I possibly could, but ultimately it is a folk-art form.