Great, thanks very much, Dwr. Only too glad to have been able to help.
When you get the pictures of Pant Dreiniog it would be much appreciated, not only by myself, if you could put some into the album; both archive and user are empty. I assume that your pictures will be archive. I'll be only too happy to then set about trying to re-take/simulate the same views, a sort of compare and contrast. Present day photographs of the site are pretty meaningless without the historical context, indeed some might find it hard to realise that there was a quarry there, as it has been so effectively obliterated, sorry, landscaped.
Yes, the rock fall at Penrhyn was quite spectacular; I thought it might happen. I'll send you a PM.