I don't plan to nominate Colditz, since halotolerant wrote me an amazing story for last Yuletide and we both now frequently write in that fandom. But promo posts 1, 2, 3, and 4, plus this picspam, are still lurking around trying to entice you. I wouldn't be sorry if someone else nominated it! More Colditz fic = yay!
AVAILABILITY: Out on DVD in the UK. Some episodes can be seen, in terrible quality, on the tube of you. (And other means are potentially available for all the television fandoms mentioned here.)
I may nominate The Wooden Horse and its prequel The Tunnel, two lightly fictionalized memoirs by Eric Williams about his experiences as a POW and his escape. They are intriguing books (try to find the unexpurgated versions rather than the ones "edited for young readers"), thoughtful, and not jingoistic, and they're massively homoerotic, too.
AVAILABILITY: The books are fairly readily available seconhand and in new re-released editions. Just be sure you're not buying the expurgated ones (check the front pages for any mention of its being edited for young readers).
Then there's the 1969 BBC series Manhunt, about a downed British pilot and two French resistance members trying, with enormous difficulty, to make their way out of France. There are 26 episodes altogether, with the show gradually expanding in scope and gaining in character depth and moral complexity. Most of the actors give fine performances, notably the brilliant Robert Hardy as Gratz, an Abwehr sergeant; Alfred Lynch as Flight Lt. Jimmy Briggs (not Jimmy Porter, despite what both Wikipedia and IMDB say; they are apparently confused by the fact that Lynch also appeared--not playing Jimmy Porter--in Look Back in Anger); Philip Madoc as Lutzig, an SS officer; and Peter Barkworth as a resistance leader codenamed Vincent. Fair warning, though: this show has a major sexism problem, which never quite stops although it is somewhat ameliorated by the eventual introduction of a recurring woman character who does more than cry, faint, and latch parasitically onto the nearest man. And I must offer a trigger warning for series 1, episode 2 for a gratuitous rape-related subplot handled terribly. You can in fact skip that episode with no harm done (and I'll note that the rape involves one-off characters, not any of the regulars). Despite its flaws, though, this is a compelling program, believably downbeat and cynical, full of three-dimensional characters. And some of the writing (especially by Vincent Tilsley--who also worked on The Prisoner--and Arden Winch) is extraordinary. Finally, a special note to Blake's 7 fans: a very young Paul Darrow is in the final episode.
AVAILABILITY: On DVD in the UK and the US.
Another fandom I might nominate is Callan, which stars Edward Woodward as the title character, a reluctant agent of a very covert British intelligence agency whose remit is not so much actual spying as dirty tricks, blackmail, and assassination. The other main characters are Toby Meres (Anthony Valentine), Callan's ruthlessly amoral fellow agent, rival, almost-friend, and person to have UST with, and Lonely (Russell Hunter), Callan's informant, protegé, semi-willing slave, and the only person to whom Callan ever shows much tenderness. There are some dud episodes, but the good ones are very good and the acting is great. The show, which aired from 1967-1972 on ITV, also includes a remarkably high number of gay male characters, who are sympathetically if sometimes patronizingly portrayed; Callan is laudably devoid of the predatory/decadent gay villain trope.
AVAILABILITY: All surviving episodes (some from the first two series are lost) are available on DVD in the UK; series 3 and 4 are available in the US on DVD and as streaming episodes from amazon.com, confusingly labelled as "set 1" (series 3) and "set 2" (series 4), but the (superior, in my opinion) black-and-white episodes from the first two series don't seem to be available here except as an import.
Finally, and on a completely different note, there's The Pirates! Band of Misfits (the original and much better UK title is The Pirates! In An Adventure With Scientists) the charming 2012 animated film from Aardman. This was badly marketed in the US and I don't think anyone saw it, but you should, because it's lovely and has Martin Freeman voicing a major character. (Also Hugh Grant, Imelda Staunton, David Tennant, and Lenny Henry in a brief role). There's much whimsy, gleeful historical liberties (Charles Darwin and his monkey butler! scary Queen Victoria!) , genre-savvy, and moderate heart-warmingness that even I liked, and I'm allergic to heart-warming.
AVAILABILITY: Just came out on DVD in the US. I have, however, learned that the US version is different from the UK version (American actors were cast in some roles, including Russel Tovey tragically replaced by Anton Yelchin, and some of the jokes were cut to be more "family friendly"); I'm hoping to get hold of the original somehow because it sounds even better.