I'm quite fussy about movies. It's somewhat hard for me to suspend disbelief and so for some reason I lucked out and can recommend Tinker, Tailor, Soldier, Spy. Not because I think it's perfectly faithful to the espionage business but because it gets the 70's down pat and that's a lot harder to do than is evident from the outside. I mentioned I enjoyed this on Facebook and a few people agreed so I'm recommending it to you.
John Hurt and Gary Oldman? You can't go wrong really but it's understated and that's a winner in spy movies. I could yawn from here into the 22nd century with the American guff they pump out from Hollywood with a few exceptions.