Geoffj,
I understand your frustrations with this nonsense. Here is some (hopefully) simple advice.
As has already been said, get the accident reference number from the police. Forward this to your insurance company. They know which police department to contact, and will be given all the details of the driver and their insurers in order to pursue a claim.
Check if you have "uninsured loss recovery" on your policy. This may allow you to get back out of pocket expenses, such as your excess and travel/hire car costs if your car is off the road.
On that subject, keep everything that will show your expenses….receipts, etc.
I know it's a pain, but a car can be replaced…at least you or someone you care about hasn't been hurt. It could have been much worse……….