Hmmm, Difficult one.
TS 156s are worth 2/5ths of sod all at the moment. Yours has exceptionally low mileage, but at the end of the day is still an X reg 156. Regardless of the mileage, if it has been outside all its life, I would assume that the floor pans have all of the problems of an X reg 156 until I had had the interior out and checked. Mileage is no guarantee of floor pan integrity, indeed if a car has been standing outside for several years, it might be a contra indicator.
Unless someone really wants a 2.0 with cloth seats, then I think you'll struggle to shift this for more than a grand. If you can find the one person who really wants to preserve a 2.0 for posterity, then you might get up to 2K for it. But you may be waiting a long time.