Thanks Gerard,
William Eustace, the blacksmith in Ballymoney was a brother of Anastasia Eustace, my great great grandmother. I believe her nephew Richard O'Brien inherited the job. I've traced William and Anastasia's father, John Eustace, to Waterford City with some links to Faithlegg House, but that's where the trail runs cold. There seems to have been some ongoing link between Waterford and Wexford Eustaces
William Eustace's wife was Margaret Sunderland (c. 1848 - 6/11/1903). Her father was Michael Sunderland - presumably your ancestors?
Found quite a bit of information here
http://www.roneustice.com/Family%20History/IrishFamiliessub/Wexford%20Families.html