Valuations are free via the PCGB, but they are either out of date very rapidly (while the market is rising for 951's it's not rising THAT rapidly) or they do not reflect market value. I used the same description and photo's with my insurer and with PCGB and got considerably differing valuations. Thankfully the insurer considers it to be higher than the club!
I will re-submit my request to the club this year to see what's changed....(the car will have changed slightly too, but not considerably for valuation purposes)
Please don't ask me what the valuations were, I'm not going to print that! Anyone wanting to hazard a guess for a half decent (not concours but looked after is how I'd describe it generally), 951 on a C plate.
A Turbo S in similar condition would go for a few £k more due to rarity perhaps?