There would need to be a full county court case taken to appeal to decide this issue. If you have pre-sold a car for a part exchange allowance of £2,000+ against a new car, and could not otherwise obtain that discount off a new car, then you could contend that your car was worth £2,000. Your insurer may counter that, as long as the wrecked car has a current Mot, tax and insurance, and has not actually been declared an insurance damage write off, then it does not matter how smashed up it is when you offer it for p/x because the allowance is being paid for it to be scrapped anyway.