Sarnie knows
But the fact is this. If you could get the car you wanted off autotrader for the price you've decided is fair based on trade values and a private value not taking options into account: You would have.
But now you are here telling us what our cars are worth: So you can't have had any success so far eh?
But if you pick up a 50k mileage non declared UK GT car for 4700 then congratulations
You would usually expect to pay a slight premium for a known member car as it is likely to be in superb condition and very well documented to compare to your average dealer. Furthermore the honesty you'll get here means chances of getting stung down the line are slashed. "You", however, seem to think enthusiast forum means bottom line price?
Good luck with the purchase anyway. I'd be inclined to sell mine for the right money, but I get the impression it'd be roughly double what you think is fair
Dave