I see that Carbisdale Castle in Sutherland was recently up for sale. For many years it was one of the Scottish Youth Hostel Association's more interesting hostels. I've stayed in it a couple of times over the years when on weekend tours up North.
http://www.rightmove.co.uk/property-for-sale/property-45743275.html
http://www.scotsman.com/lifestyle/heritage/former-hostel-carbisdale-castle-close-to-sale-1-3632733
http://www.rightmove.co.uk/property-for-sale/property-45743275.html
http://www.scotsman.com/lifestyle/heritage/former-hostel-carbisdale-castle-close-to-sale-1-3632733


- cracking position. We were allowed up the tower by the warden - for even better view.