I too saw the original at the flicks in 1977, in the Tottenham Court Road Odeon during a visit to the Smoke. Very enjoyable, particularly the special effects which were outstanding for the time.
That splendid actor Peter Cushing – he of numerous Hammer Horror films – played a typically creepy character in it; he was also Dr Who in two rather poor film spin-offs in the mid ’60s
I’ve also seen the two early sequels: The Empire Strikes Back and Return of the Jedi, though both of those on the goggler. Good fun too.
Not seen any of the later ones.