I never watched the series, but listening to the theme song just now it seems to owe something to the music-hall standard, 'Oh Mr Porter'.

It is absolutely a filk of "Oh! Mr Porter," which is why it is so catchy.

(spatch went through a phase of David Croft earlier this year and watched Hi-de-Hi!, You Rang, M'Lord?, and Oh, Doctor Beeching! which I did not all watch with him because from that much television I would implode, but I did learn the theme songs.)