Not in the UK, but the events leading up to the Ludlow Massacre is a good example of this. The Colorado Fuel and Iron Company hired a "detective agency" (more like thugs) to break a miners strike. The detectives armored a car and put a machine gun on it and fired at the strikers. Not only that, every once and a while, they'd just randomly fire a bullet at the tents where the miners lived, sometimes killing someone. Hope that helped.
Sorry I can't up vote, but I don't have 15 rep.