I share John's voice of concern.
I don't know what a cherished early Roadster is worth today, but in my view this one is essentially a "barn find" and I'd want to pay at least £5k less than the market price for on with 15,000 miles on it and an annual service history.
My Boxster had been first registered in late 2016 and had run just 11.000 miles, with less than 1000 miles in the last 18 months. It had a full service history and MOT trail. It was sold as a Porsche Approved Pre-owned car with a full 2 year Porsche warranty, exactly the same as the new vehicle warranty.
Even so on top of the 111 point Approved Pre-owned check the car was given a main service, including a brake fluid change, plus new pads and discs and tyres on all corners, because of concerns about degradation of the brakes and the age of the tyres: my estimate is that the dealer put almost £3k into it to bring it up to standard.
Yes, I paid a top price £52,000; but I have a car that is little different from a new £80,000 Boxster S.
