1) Forget Chipsaway. They do small individual blemishes. You will want all three panels resprayed, in the correct conditions, not on your drive
2) Try to speak to others that were there to find out if their cars were damaged, or at least get them to agree that they thought he was being a bellend.
3) It seems like you have been (don't take this the wrong way) a bit of a pussy. It sounds like you have been far too civil. Before turning up on his doorstep, I would phone him and tell him your intentions of getting a quote from a bodyshop which will be at his expense. If it was me, the guy would have left, knowing that in no uncertain terms, that he was going to be paying to repair my car.
4) Turn up at his house with your mutual friend and deliver the quote. If he refuses to pay, get a solicitor to send him a stern letter, it's amazing what affect these can have!