Hiya Clannessie,
I do not have a lot of information for you. I looked up Moy and Charlemont in the 1852 Directory of Belfast and Province of Ulster. Your mention that one of William's sisters ran an Inn made me wonder if any Taylors might be in the Directory. Sure enough there was a George Taylor who was a publican at Charlemont. Moy and Charlemont are two little towns, really one town, divided by the river Blackwater. A search through later directories may disclose the name of the sister who ran the Inn.
All the Best, Christopher