Ideally i would look for a way to have your insurance cover it - roof storage box falling off or contents falling out??

failing that I would...

Speak to the guy and say that the very best he can do is give him 2k cash in his pocket and let him claim off his insurance, this will cover the excess, the increase in premium and still leave him a grand I would think.

You mate has been good enought to seek the guy out and try and sort it, but the guy with th ebeemer needs to have an incentive to work with your mate to a quick simple solution.

If they guy in the beemer takes an arse, it may be worth your mate reminding him that 90% of people would have driven off and to cut him some slack for a genuine accident.

Bit of give and take.