I owned a valver new in the early 90's. Speaking from experience, the cars that were on sale then, compared with even the mintest higher mileage examples now are not comparable. I drove alot of valver and looked at even more before i ended up getting my 172. To be honest (and no disrespect to anyone with a valver), even the 3k examples were tired and lame, compared to my new one in 1993. No comparison. You just cant knock miles off a car no matter how much money you spend.
The chances are anyone who buys this wont be interested in traffic light grand prix or proving his dad is bigger than your dad. He will be a collector. And to a collector it is worth that simply because, there are no real alternatives on the market. Its not like the market is flooded with Williams on 8k miles. Therfore it s a sellers market. My father followed the sale of the first williams off the Bohnhams web site and thought that the cars value (if he sold it) would be around 20 to 25k.
My father traded classic and collectable cars for some time (not the usual s**t, but very rare and hard to find cars), and when you realise someone will pay 80k for an ex rally car gordini that ragnotti once sat in, or 40k for a 5 Turbo 2 in good but not great shape, you begin to realise 10k for a clio williams is not that much.
If its as described on ebay a few months back then it is worth 10 k to someone. If i had the cash id would buy it, but my budget was only 5k, hence i got a 172.