Truth or Dare

This is a British movie about a group of teens who while at a party, play a game of 'Truth or Dare', but the game gets out of hand when one of the party goers (Felix) is picked on by the other teens. A few months later they are all invited to a party that Felix is throwing at his parents mansion. But when they get there they are told the party is in a cabin further up the road. They arrive to find that Felix's brother is there instead, but where is Felix, and what does his brother have in store?