Back in the early 60's I guess, my father Keith Bird and a number of other professional musicians appeared in a Michael Bentine TV film about two military bands, one German the other British, who become left behind at the front and try to out play each other. Both band's members were played by the same musicians. I have photos taken on the set but otherwise I know very little.
Hi - I did reply to this via email but you might not have received the response
From your description of the film it sounds as though it might have been a filmed insert for Bentine's television series It's A Square World - it certainly sounds as though it'd fit in to that format.
However, there are some other alternatives: After Hours made between 1958 and 1959 included many filmed inserts. In 1960 Bentine wrote and starred in a stage play "Don't Shoot, We're English." I can't find a record of it being filmed. All Square was broadcast between 1966 and 1967.
I remember seeing this sketch at the time, and I'm pretty sure it was in It's a Square World in the 1950s. The reason I think this, is that I left to work in Germany in 1964 so saw very little British TV in the 60s and 70s. One of the jokes was that while the Germans were kitted out with every kind of high quality instrument imaginable, the British Army was marching up and down while playing comb and paper.