Only thing I would say is that if the gun is shooting well and you are confident in it, then a service will necessarily push the sale price higher. You might consider leaving that choice to the potential buyer.
I paid £800 for one last year and got a great one, though as a lefty I had to buy a grip. A large or medium RH grip is best for selling as they will suit most buyers. £900 un-serviced, £1000 -ish serviced?