BBC Four is the best TV channel I do not have access to. Their music documentaries are frequently wonderful (when I have the chance to catch them on the Internet). It is hard to say which I enjoyed more: Synth Brittania, Keep On Running, Hotel California (more on this one later) etc.
This link list all (359) their music programs ever broadcast. On a quick search I found a dozen which seem very interesting: BBC Four Programmes – Categorised as Music.