Thank you both for your replies.
It looks best to leave the Maesmore connection for now as I can find nothing conclusive.
I looked at the will of John David, d. 1730, Faerdref Ucha (perhaps a brother to William David John, the son-in-law of John and Gwen Jones), and he mentions his cousin Elizabeth ffoulkes and her children 'John Jones, ffoulke Jones, Thomas Jones, Philip Jones, Robert Jones, Mary Jones, Catherine Jones', by husband Thomas Jones, Ty Ucha. In the parish records this is Ty Ucha, Faerdref. His father John Jones (d. 1705) is given as of Faerdref - I think he must be the cousin then of Maurice Jones, who had referred to a John Jones, Ty Ucha, Tyfos....perhaps the two townships are nearby and linked (I can find no boundaries for where Faerdref is supposed to be sited within the parish).
Also, this gives the names of several more children which I did not know about, and I wonder if either of them are the father of either a Rowland Jones, or Griffith Jones. Rowland, as I have mentioned was parish clerk before Thomas, and as this seems to have been almost a hereditary office, I have often wondered if Rowland was a relation - there's nothing likely in the Llandrillo parish records however. Likewise a Griffith Jones is shown as living at Plas Adda when he died in 1770, so I wonder if he was a relation.
I cannot establish exactly how John David is a cousin of Elizabeth ffoulkes, and whether he is perhaps also a relation to Thomas (both of Faerdref). Elizabeth as you noted previously was the daughter of Foulke Morgan and Catherine ferch Thomas. I have a feeling Foulke Morgan is somehow related to the John Foulkes of Cilan whose daughter married Ellen Foulkes, Gabriel Jones, and perhaps related to the Joneses in some way.