What could I say to the law about this?
Can I give you an honest opinion, strictly in a personal capacity...
By the fact you were shouting words to the effect of tosser our of the window, and racing ahead to try and get him to pull into a car-park - proably won't be viewed too kindly. You've at minimum commited a public order offence - and I guess the potential for driving offences on top...
The best thing you could have probably done, is pull over as soon as it's safe, and get yourself out of danger. Then call it in, if you deem it necessary and get the VRM.
Sounds like six of one, half a dozen of the other.....
If you'd have kept your cool and not "bitten" maybe you could have reported him, but as it stands, probably best to just put it down to experience and learn from it.
No offence intended mate - just a balanced opinion.
I have done simelar things in the past, and been offered simelar advice
