Is yours a bench rest version or standing match target? If its a match target I would advertise it on the Stirton site as that is purely match target orientated. They do seem to go closer to £11000/£1000 but as yours is so new try higher, worth a start at £1500.
Sorry to hear your wife has arthritus, I hope it settles down, it stopped me pistol shooting, but I find with a good modern jacket and shooting trousers I can still shoot rifle to a reasonable standard, one way the modern rules has helped us old farts keep shooting.
Good Luck
Robin
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?