Hi again Bruce.
No sooner than I leave the computer I pick up a book with more info.
From "Historic Houses of Pembrokeshire"
...In 1785, Herbert Lloyd of Carmarthen....sold the lordship or manor of
Hayston, the capital messuage and lands called Hayston and a messuage
with Hayston Mill, to Richard Mathias of Tierston, Steynton parish. In
1786, three properties at Hayston were owned by Richard Mathias,
Reverend Dr. Phillips and Lord Kensington, all let to tenants.........
In 1837 appeared particulars of sale of the mansion house and land
called Hayston, late residence of Richard Mathias Esq., deceased, the
manor of Hayston, tithes of the whole estate, and the corn grist mill
called Hayston Mill.....
That last bit confirms what I wrote in my previous reply.