I would offer caution here, standing up to someone is one thing busting windows is pretty lame.
Brake fluid on the other hand or if its a diesel an old golf ball in the tank will cost a LOT more, and the golf ball will cause far more inconvenience, just remember to spit the outer skin so it works quicker, you may be happy to wait 6 months?.
My parents were involved in a situation years ago when they were hit from behind, owner of said BMW swapped addresses and said they would send the details, with a witness. Sufficient damage to nigh on write off a 2 year old Metro.
They ended up with nowt, the response from BMW man was 'Prove it', no damage to the BMW. Just the word of the witness, case busted. My old man is not the shy type (his claim to fame is being barred from every pub in northampton in his youth)to take things lying down so i would have been very surprised if this gent hadn't 'tripped on the stairs' at some point in time later.
But he still ended up fixing it himself.
I hope it goes well but i for one would not be holding my breath.