Glengarriff came up trumps with Wilson's Filmy-fern. I was sure this must be there but found that the Tunbridge Filmy-fern I stumbled upon a few years ago, when I hardly knew what they were, is very much dominant there. (In places the plant is abundant.)
The identifcation is hard as well but, as usual, once I found it I realised straight away that this was "significantly different" - and there is only one other species in the genus in the UK.
They were growing together with Wilson's higher up the tree trunk on which I found them. To me the longer vein cells were more diagnostic than the vein ends being at the end of the frond - I find that even with a x10 lens the vein ends of the Tunbridge fern are often at the end of the leaf to my eyes.