As above, do some legwork and find adverts for similar age/condition models of your car and then submit these to the insurers stating what you think it is worth. They have a duty to mitigate their losses but if you can prove they have offered below true value then they will negotiate. I had exactly this issue with a car previously so my full sympathy to you!Sorry to hear your loss, seems a little excessive though. If you don't think it's fair value, I'd try and find a number of examples (autotrader/ ebay) around the value you believe is more realistic for your age and mileage.