What Earl said. Good reactions. If say they were colluding via mobile phones - can the police seize their records and use it as evidence. Innocent until proven guilty etc, but this looks..well you know, a bit suspicious to say the lest. Did the silver car not take the same exit as you? Perhaps they wanted to remonstrate with the black car driver? Well, I think a significant find here might just be the claim they make in the event a collision does occur - it will be more than coincidence if these two other cars are involved, won't it..
Nice bit of breaking you did there buddy, Report that bastard to the police and make sure you show them this footage