A similar thing happened to me a few years ago. A post office van crashed into my car while it was parkedon the road. I contacted the post office's insurers (driver left the details) and they arranged for me to have a very nice courtesy car for a few weeks and they valued my vehicle (prior to crash!) while I had the courtesy car. They valued it at a bit less than it was actually worth (which wasnt much) and I took the money and bought a new one. I think you could probably claim (if you are fully comp) on your own insurance - less excess - for the difference between what their insurance company values your car at and what its worth - or let them argue it out. That is if the driver was insured. Otherwise you'll have to claim on your own insurance (if you are fully comp) less excess. Or go through some scheme that pays out on behalf of uninsured drivers. Cant remember what its called but its a pot of money that all insurers pay into to.