Don't think you can force a cinema to do anything it doesn't want to do. You can't force it to show any particular movie, if the owners of the cinema (and remember, Cineworld is not owned by the manager at that particular branch, but by Cineworld's head office) decide they don't want to show it.
If Cineworld think it is not financially viable to show a 2D version of a movie when they are already showing the 3D version, nobody can make them do it. If they think that there will not be enough people paying to see the 2D version, and they will make more money by showing an alternative movie to Star Trek in the other screens, then that is entirely up to them. If you want to see it in 2D, find an alternative cinema in your area which is showing it in 2D.
This makes sense, annoyingly. I just personally don't think it's on...but businesses make their own decisions and like you say, I can go elsewhere if I don't like it. 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?