Hi
Forgot to point out previously that Penrhyn is in Merionethshire; it's only 3 miles from Porthmadog, which is in Caernarvonshire.
Have spoken to 3 natives of Penrhyn, ages ranging from 70 to 80 yrs old, 2 of them still living in the area. There is a place off High Street known as yr Hen Bost (The Old Post), but the Post in the period you're talking about was in Bank Place(Bro Einion)/Church Street. After the period you refer to, the Post was still run by the same family, they think it was the daughter and son in law, surname Williams(?). They've given me names of 2 family members, one who has died, and another who they think is living in Anglesey; the family apparently had an Anglesey connection. Does this info make sense ?
My contacts have promised to make enquiries.
Emyr