RAC have severely damaged my car, help!

NameUnavailable

You need to get the garage to provide a written estimate of the repair costs and then send that to the RAC with a demand for payment.

If they refuse then open a small claims case.

There is an issue of betterment to consider i.e. if the garage are fitting new parts then you are ending up with a 'better' car and maybe can't expect the total cost (so the idea of used parts is good if your garage can do that).