The Guardian has a piece on the best double bill of British films. One suggestion was The Devils and Black Narcissus.
Someone also says The Wicker Man was released as the B-Feature for Don't Look Now.
Ones I liked:
Theatre of Blood and The Abdominal Dr Phibes
Gregory's Girl. Twice
Kes coupled with Gregory's Girl (actually Gregory's Girl gets mentioned a lot)
Brazil and Blade Runner
www.guardian.co.uk/film/filmblog/2012/nov/09/open-thread-cult-british-films