What any half decent arse-licker should strive to attain. The origins of becoming a Knight are enshrined in the mists of time. If the mental image you have of a Knight is some stout-hearted merrie yeoman being mayde a knighte of the realme for grayte service to Hif Majefty then you'll be somewhat deflated to learn that these days knighthoods are blatantly flogged off for simply swelling the coffers of the political party incumbent - in particular Neu Arbiet.
Knighthoods come in two distinct sizes: Knight Bachelor and knight of a specific Order of Chivalry. The senior grades of which entitle the member of the order to call himself 'Sir' - that's 'Sir' as in Lancelot, not as in 'It wasn't me sir, it was Higgins that left the turd in your desk!' A Knight Bachelor doesn't mean the knight is unmarried, but rather his knighthood is independent of any order. He does get to wear a nice medal-type-thing and an invite to tea & cakes at the big house.
Holders of the MBE and OBE are not knights of the Order of the British Empire and are not 'Sirs'. They are, however, 'Sirs' when your standing in front of them in your GMS during an Interview Without Coffee. Don't try telling them that they're not really a 'Sir' as this will only deepen the hole you're standing in.