I know it is annoying to ask, but I need help with a horror film title. I watched this movie at the dead of night, almost ten years ago. It seemed british/uk to me, as everyone seemed to have an accent.

The plot, from what I can remember, is a group of friends are in a large house/estate in the countryside. At the beginning of the film, its announced that a group of people have been murdering people and filming it, and they call themselves by a particular name, but I can't remember the name. The group of friends are murdered one by one, until its revealed one of the friends is part of this group and has been the one murdering everyone. I know at one point they end up at a movie theater and the serial killer cult are in the theater. The scenes were somewhat bloody, and the movie seemed pretty recent.

I know that was a weird plot, but it is all I can remember. If anyone can help with the title I would like to check it out again.