Do you live/travel anywhere near Llanfachreth, Meironnydd? TECHNICALLY in the modern borders of Snowdonia. There's a cottage there near the trails, west of the Glasdir mine, called Ty'n-y-buarth. I THINK it's no longer being lived in. Anyway it's between a few rivers(the western one being the Afon Mawddach) and one has a bridge over it called the Pont-y-Pabi that has a legend about it a witch rescuing her baby from the fairies who live under it. If you ever see that bridge/cottage, snap a pic??