I was driving in middle lane towards a roundabout in heavy traffic and someone in outside lane started drifting over so I moved slightly over and clipped this persons mirror. I was slowing down as I was approaching a roundabout and was doing appx 23mph or even less. There was nowhere to stop and I noticed my wing mirror was fine so I carried on. The man came alongside me swearing and yelling at me and I was extremely scared as he was threatening to follow me. He'd said I'd ripped his wing mirror off but it looked fine and was still attached. When I was stopped at lights, I rang 999 and put them on loudspeaker. I said what had happened and they asked me where I was and I said, Carlton St, heading towards the sea front. They asked me to come to the police station and I did but I had to run into the building with the man still swearing at me. As he was so abusive, they took us into separate rooms and the staff exchanged the details. We left separately and I was escorted by security (just for my security) to my car. Do I really need to call my insurance company for something so minor as a mirror? Can I use his "road range against him