Hi Greencode,
I appreciate that your car was parked & unattended when it was hit and that you are the innocent party. However, my advice would be to report it ASAP to comply with the legislation. The police can then serve a form on the registered owner of the offending vehicle requesting details of the driver at the specific time. I believe this will make your claim against THEIR insurance easier to cover the costs of your repair etc.
Good luck. Chas.