Mulla, you need to ...

a) check out what the average price for the same car is local to you and collect a selection of say 15 examples

b) look at parkers price guides etc for what they are claiming it will be worth.

This will gived you an idea of what they will be offering - to what it will cost to replace if you wanted to,.

Finally, in our case it was the inspector that priced the car, my sister kept sweety sweet with him and he up'd the offer prrice from 4k to £4500 after she said she wasn't happy and that the cars he was suggesting as comparision were not in the same league.

Currently about to do it all again from her crash today!