Anthony Head. A few years ago I was on a train with him from mid Wales to London (I think he was filming Dr Who) which broke down at Newport, Gwent. We were told we'd be stuck for hours so all the passengers piled into the Yates' Wine Lodge next to the station. The staff were gobsmacked that Giles from Buffy had wandered in and kept trying to buy him drinks, and he was lovely and kept insisting he should buy his own.
Ed Miliband and Justine - met them 'off duty' at a friend's party a few years ago and they were both lovely.
Richard Wilson (Victor Meldrew) - sweet man, not at all like Victor!
Charles Kennedy - lovely, but v drunk and incapable and clearly struggling at the time. 
Cherie Blair - said my DS was a 'beautiful baby' so of course she's fab and has exquisite taste 
Salman Rushdie - nice but shy.
Tessa Sanderson, my childhood sporting hero - met her twice and totally vile both times. So horrible to 'little people'. Definitely would fail the waitress test. Gutted. (I also admired Fatima Whitbred so will run away if I ever see her, as I now know you should never meet your heroes!)
Matthew Parris - Times journo, Polly Toynbee and Michael White Guardian journos, all lovely and very polite and professional. Witnessed Michael White (who is v small) step in to stop a large obnoxious drunk being abusive to the person serving him. More junior national newspaper journos can be a bit 'don't you know who I am?' but they were always great.