Inspired by this article

http://www.ultraculture.co.uk/11883-something-needs-to-be-done-about-the-putney-odeon.htm

Best

BFI (obviously)
Cornerhouse - Manchester (friendly knowledgeable staff who don't shrug when you point out the ratio is wrong)
FACT - Liverpool (so comfy and in an ace building)
Riverside Studios - Hammersmith
Screen 1 in the Haymarket Cineworld (although I have seen a rat there in the past)
Rio in Dalston - excellent Sunday double bills

The worst

Chester Cineworld - the heating broke down on a January evening and they didn't think to mention it until tickets were purchased and refused to give a refund
Genesis in Whitechapel is also in dire need of a refurb (quite fond of it though still in a weird way)
The Cineworld in Shaftsbury Avenue - staffed by utter cretins.