Stayed at Stonefield Castle Hotel in Tarbert (Kintyre), Scotland; you may find my full review in the reviews section of this website.
In some ways it was really lovely; it's situated with a beautiful view of Loch Fyne and is known for its gardens, which were in bloom when we were there in May. On the downside, the plumbing in our room was problematic and the carpeting, drapes, paint condition etc. throughout the property were somewhat worn. They mixed up my reservation so that I would have paid about 10% more if I had not gone down to the desk with my original receipt and made them recalculate.
Stonefield was never really a castle but rather a country house (albeit a really nice one) built around the time Queen Victoria ascended the throne. It has been a hotel since ca. 1970 and has remodeling reflecting that period. I would have enjoyed it more if they'd provided some background on who built it and who lived there over the decades before it became a hotel.