Where is it you live? If it's anywhere near Atlanta I might drop in next
time I visit my brother in Forsyth County!
Hayston Mill is in the northern part of Llanstadwell parish, almost on
the border with Rosemarket parish. The map reference, if you have an
Ordnance Survey map, is SM 937086 and the mill is marked on both the
1:50,000 and 1:25,000 scale maps. It is close to Hayston Hall, but
whether there is any connection between the two places (apart from the
physical ones of a dirt track and a small stream) remains to be seen.
The only miller I imagine there would be in the area is a corn miller. I
am sure the mill is no longer in use.
In the 1891 census the building was described as Hayson Mill and the
miller was called George Cole (born Nolton parish, Pem).
I think the road from Johnston to Llanstadwell is called Hayston Road
and there is a Hayston Mountain. Why there are so many places in south
Pembrokeshire with the suffix Mountain when they could hardly be even
described as a mound I really would like an answer to.
In a very small area we find Hayston Mountain, Nash Mountain, Hill
Mountain (!), Hearson Mountain, Newton Mountain, Burton Mountain and
Williamston Mountain. There are a few "Mountains" in other southerly
parts of Pembrokeshire, but not in the hilly (I hesitate to use the word
mountainous when the highest point is, I think, 536 metres [1,760 feet]
above sea level) northern part of the county.
Good luck with your search.