The insurance will offer you a low amount at first , they allways do this as often they get away with it. just reject the first offer and they will make a better one. As has been said look on Autotrader for cars as similar to yours as possible and see what price they went for, use the prices you find as a guide what to accept from the insurance. Remember the insurance have to pay for your out of pocket expenses , ( loss of earnings,fares, taxis, car hire etc) as well and if the accident was not your fault you claim for loss of NCB in addition.