Forum Rider Down and/or notification of minor incidents

I had an incident recently where a driver out of nowhere overtook me yelling and hit the brakes directly in front of me, resulting in me hitting him, but luckily only with enough force to lift my back wheel up slightly.
As I pulled over to the pavement to examine my bike he hops out of his car, yelling and screaming runs over to me, grabs my bicycle out of my hands and throws it across the pavement.
His friend hops out of the car and holds him back from attacking me, and when the driver finally calms down he looks at his rear bumper, claims it's damaged and begins to get aggressive again.
At this point I'm completely intimidated and tell him that I just want to do the right thing, and agree, against my will, to £20 damages (£40 for his bumper minus £20 for damage to my bike).
It's all quite ridiculous anyway since he caused the accident and then assaulted me, but I give him my contact details as I have no cash on me.
Instead of dropping it, yesterday he contacts me, having Googled to find my email address, and claims £300 damage to his bumper.

Firstly, what is wrong with people ... all this happened in front of children in the back seat of the car, is this how you teach children to behave?
Secondly, is there any way to make this all go away. I don't want damages, I just want this cock to drop it.

If this is genuinely what happened, then stick to your guns and take him to court. It sounds like a variant on the insurance scam of cranking the brakes on when in front of another driver and then claiming whiplash injuries etc. Scary business though.