Firstly, do not go through the third party insurer directly because it is a conflict of interest. The at-fault insurer acts as it's own paymaster to someone they are not in contract with. Secondly, have they valued the car correctly? Get your own value by someone who has access to Glass Evaluator or CAP motor research. Find a friendly car dealership, and see if they will do for you. Then try to get the insurer to increase the value. Is your car a total loss, i.e. do the repair costs exceed the market value? If not, force them to repair it. A car is not a total loss unless the repair cost exceeds the market value. Also bare in mind, your car may not be worth as much as you think it is. Find a similar model for sale online (similar year, mileage and specification as to the one you had). Use that as evidence to support what you feel the vehicle is worth.