Firstly, a big "thank you" to those who have replied to my initial enquiry. I think (hope) I have solved the problem ...
John Davies' son David (1827-1899) ran The Plough Innn in Felingwm Uchaf as did his son Walter. In the census, Felingwm Uchaf is described as "the hamlet of Meiros" in the parish of Llanegwad even though it is the former that had the pub, shop, etc. On the Bartholomew's map, that I found thanks to Hanes Teulu's link, Crug las is shown 2½km to the west of Felingwm Uchaf. However, on the modern OS, it is identified as "Bryneiddan" at GR 485248.
I am assuming this is Criglas Uchaf until my next visit when I'll knock on the door and ask!