The general rule of thumb is to reduce the value by 20% from a retail figure, if it has a previous categorisation attached. It does also depend on whether the vehicle has pre-existing damage - did you repair the old damage and what standard was it done too? If it is a poor job, then it may well only be worth £1000, if it was done to an impeccable standard, I would expect the value to around the £2500 mark. You can always dispute the value. If you are dealing with the at fault party directly, you may well have shot yourself in the foot though, as you cannot escalate to the Financial Ombudsmen service.