Very well spotted Yorkie, I passed it on a walk yesterday and Googled it when I got home. It was built about 1870 by the then MP and Lord Lieutenant of Ynys Mon and converted to a special-needs residential school in 1950 at a cost of £15,000. When it needed updating to all the new health and safety regulations in 2000 the cost was estimated at £2m and annual running costs were running at £800,000, so the councils (it served Gwynedd, Aberconwy and Ynys Mon) closed it in 2012.