So yes I now its my fault, got out and apolgised. It was a very slight bump as I'd only travelled about 10cm before I hit him.
I look at the cars and can't see any damage to either car.
I have a small Yaris which is pretty much vertical at the back apart from a low down bumper. Bloke is ranting at me and points out 2 large horizontal scratches on his bonnet - on the flat bit of his bonnet which is way higher than my bumper. He has no damage to his bumper which sticks out 6 inches further than where the scratches are, no damage to his number plate, no damage to the vertical grill bit. I really think he's trying it on. The scratches even look like they're going rusty inside. His car is 19 years old Peugeot and the whole bonnet looks like the paint is beginning to crack through age and these "scratches" look more like that. I gave him my mobile number, he didn't want to give me his. I've taken photos of the damage. Even the security guard said it didn't look like the damage was caused by my car.
So what do I do if he rings up - tell him to go jump (as dh says) or give him my insurance details?
Also a friend of mine reckons that if you have a bump in a private carpark you don't have to provide insurance details or pay for any damage even if it is your fault. If I thought I'd damaged it I'd pay, but really can't see how my car could have.