Pretty rubbish to be honest, although I do have to ask why your first impression was to post on the forum, as my first action would have been knocking on the door, there's absolutely no way they can dispute that, and by saying 'me and my wife' saw you hit my car, and we have taken photographs of the damage to yours and mine, it would give you enough proof to point the finger.
If they became nasty about it then I don't see any reason why their insurance can't be claimed? Surely its just as bad as being reversed into at a slow speed and leaving a mark? If they dispute liability then insurance can provide ways of having the paint tested.
But would deffo be banging on that door right about now, while both cars are sitting side by side.