I don't think the UK will let go of them... Strategically, Scapa Flow is incredibly important and played a huge part in both world wars.
This is a quite clever publicity drive to get some more money, nothing more. Good luck to them - although I recently visited and the roads were in better condition than those in my county in England, and the ferry services (Except Pentland was still down) were excellent. Quality of living looked (admittedly, through the eyes of an outsider in summer) pretty good too, certainly equal to similar rural parts of Cornwall and large areas of Wales)