Some really 'lesser known' ones off the top of my head:
-A Cottage on Dartmoor (The best British silent film - Absolute must see)
-The Living Dead at Manchester Morgue
-The System
-I'll Never Forget What's'isname
More well known:
-The Abominable Dr. Phibes
-Theatre of Blood
-Peeping Tom
-Night of the Demon
-Brief Encounter
-All 'Ealing Comedies' - especially Passport to Pimlico
-School For Scoundrels
-The Loneliness of the Long Distance Runner
-Billy Liar
-Saturday Night, Sunday Morning
-The Devils
-The Ipcress File
-Blow Up
-Kill List