In theory, the valuation is about right in terms of like-for-like pricing - it's just that there aren't any about! Older, newer, more miles or less, or located hundreds of miles away - yet they seem such a common motor!!
Interesting side-note....I told the assessor at the beginning that I wanted to keep the stereo as it is an after-market unit with a USB socket. He said that the car was being assessed "as-is" and he would deduct £50 from the valuation if I took it (cheek!).
Anyway, when he revised the valuation and I agreed it, he rang it in to HQ, then when I spoke to him later asking when I could remove the stereo, he admitted that he'd forgotten the deduction, so could I please replace the original stereo.
Luckily for him I had kept it. Unluckily for whoever gets that car, that stereo is bu99ered. Luckily for me I get to keep the stereo (with all the remote-control wiring adapters) AND my £50.