Takes a couple of days to come up on iPlayer IIRC. And isn't this the third time it's been on? I watched the original, and I'm sure I've seen a repeat (of the original, not the crass remake that was made, maybe as a film).
What I find amazing about it is that, although the finale is incredible, one can suspend belief and be drawn in to the moment.
And I've also still got Smiley's People to re-watch!.