Luckily I have a choice of three or four cinemas I can go to but many people are stuck with just one within reasonable distance. This is where discrimination on the cinemas part could come into play, maybe?
Unlikely. Nobody could force your village pub - if there was only one - to serve Stella, if that was the only lager you liked. You couldn't claim they were discriminating against you by only serving Carlsberg and Becks, which you don't like. Nobody is forcing you to drink Carlsberg or Becks, they are on offer if you want them. And likewise, nobody is forcing you to go to the cinema to watch a movie in a format you don't like.
Why should any cinema show any movie, if they don't want to? And what rights would any prospective customer have, to say that the cinema is discriminating against them because they aren't showing a movie that the customer wants to see, or aren't showing it in a format that the customer wants to see it in?
Cineworld are showing a particular movie, in a particular format, and inviting customers to come and see it if they want to. Nobody is making anybody go see it if they don't want to. But certainly nobody could sue Cineworld for discrimination just because they don't want to go see it. And nobody could make Cineworld show it. Cineworld show movies that they think will make them a profit. You can't force them to show a movie which they think will make them a loss.