I'd expect people to have seen many of these:
10 Rillington Place – Richard Attenborough as serial killer and necrophile.
Abominable Dr. Phibes, The – Vincent Price camp classic
And Now for Something Completely Different – Monty Python sketches
Anderson Tapes, The – Connery robbery while being watched
Andromeda Strain, The – Michael Crichton adaptation
Bedknobs and Broomsticks – Disney mix of live action and animation
Beguiled, The – Clint Eastwood gets interesting #1
Carnal Knowledge – Mike Nicholls directs Nicholson
Clockwork Orange, A – Kubrick masterpiece
Devils, The – Ken Russell goes mad
Diamonds Are Forever – my favourite Bond
Dirty Harry – Clint Eastwood shoots people
Duel – Spielberg's breakthrough
Fiddler on the Roof – Topol musical
French Connection, The – with the best car chase, ever
Get Carter – One of Michael Caine's finest
Growing Up: A New Approach to Sex Education, No. 1 – Martin Cole shows real live sex
Harold and Maude – he's obsessed with death, she's dying
Johnny Wadd – John Holmes + plot: why Boogie Nights was made
Kidnapped – Michael Caine does a decent Stevenson adaptation
Klute – Donald Sutherland + Jane Fonda
Last Picture Show, The – Bogdanovich's best
Le Mans – Steve McQueen + cars
Mary, Queen of Scots – Vanessa Redgrave & Glenda Jackson
Morte a Venezia – aka Death in Venice
Pink Narcissus – gay classic
Play Misty for Me – Clint Eastwood gets interesting #2
Rouge aux lèvres, Le – aka Daughters of Darkness, classic lesbian vampire
Shaft – John Shaft!
Sunday Bloody Sunday – Jackson again, bi classic
THX 1138 – When Lucas could do plots
Trafic – Monsieur Hulot
Tragedy of Macbeth, The – Polanski's version
Unman, Wittering and Zigo – aren't British public schools great.. for murder.
Up Pompeii – film version of titterful UK TV sitcom
Willy Wonka & the Chocolate Factory – the original
(The only two I haven't seen – but would pay to do so – are Johnny Wadd and the Martin Cole sex ed. All the rest are worth watching.)
But none of these was apparently #1 at the UK box office that year.
What do you think was?
(Update: and even if you don't want to guess, how many have you seen?)