Tell the insurers, I recently had an accident (someone drove into the side of me as I was driving around a roundabout) person wanted to settle it cash, but when he got the bill decided I drove into him and its all a mess.
The sorting it out cash never works out, as people think that £100 will sort out any damage, and it won't
Had virtually the same issue. Woman ploughs into wife's Smart car in a car park. We're shopping and the cars parked. Woman driving a Mercedes ML, virtually no damage to hers, plenty of damage to ours. Husband calls after 4 days saying "probably don't need insurance to be involved, get a quote and we'll sort it out"
Got the quote, over 1200 quid, suddenly the back peddling starts and lots of "its a Smart car, how does it cost that much, take it to another garage blah blah blah!!!" Unfortunately he didn't take into account that Smart are Mercedes and don't get the half price because it's half a car.
Go through insurance every time, that's what you pay for and everyone is friendly until they realise it'll be more than £50