Found this article on Wikipedia: https://en.m.wikipedia.org/wiki/Closed_cinemas_in_Kingston_upon_Hull Which rather impressively had its genesis from a thread on Not606! https://www.not606.com/threads/hull-cinemas.38551/
Ahh Now we’re getting somewhere for my question Was it also run as a club/disco around a similar time too? (Arthur’s? early 80’s?)
They both showed "X certificate" films, which would be called "soft porn" nowadays. A friend used to watch them back in the 70s.