Brighton Rock, A Matter of Life & Death and the Third Man are all absolute classics.
As is Black Narcissus, which must be the only U-rated film ever made about sexually frustrated nuns... (if you steer clear of The Sound of Music - which I usually prefer to.)
Withnail & I and 24 Hour Party People get my vote of the more recent batch.
Circus
Fever Pitch
Lock Stock and Two Smoking Barrells
Snatch
The Long Good Friday
Mona Lisa
The Italian Job
Mrs. Brown
Reach For The Sky
The Day The Earth Caught Fire
I'm Alright Jack
The Chain
The Knowlegede
The Ladykillers
Get Carter
Croupier
My Kingdom
Brassed Off
Little Voice
Four Weddings & a Funeral
The Full Monty
About A Boy
Quadrophenia
Arthur's Dyke
Hell Drivers
and last but not least....Conspiracy.
I love British films. We make stories, not special effects, with a set of links inbetween.