Thanks Hugo, I hadn't heard of Castell Tremlyd. The village, or more accurately, hamlet, was said to have been right on the sea part way round the Orme. I have seen a picture of it which indicated it was tiny with only a small number of inhabitants. As I recall, it was said to have been abandoned long ago. Quite how long ago, I cannot recall for sure.
From memory, the access was from the sea mainly. I imagine there must have been some land route but am not sure.
This is one matter which I read about some years ago and always meant to pursue, then never did. Such is life...
Helig