The BBC are supposed to have an online shop now for past shows that aren't on iPlayer .. but that show isn't available, which I find amusing-annoying considering you can get it on Amazon. http://www.bbc.co.uk/programmes/b04xshqd has some clips.
But it's not just about overseas. I as a British citizen who has paid his (last) TV license have quite literally already paid for this content - yet to watch it outside of the iplayer window, I still need to buy it.
I just found it on a torrent site. As a British citizen and license fee payer I don't have any moral issue with torrenting it. Interesting to think about, actually.