Thanks for the information on the searches, I will look into it.
As far as people of welsh origins are concerned I believe the National Library of Wales have done a lot of work with the Church of Latter Day Saints who have been involved in archiving a lot of US family history records. I am assuming that the sharing of data has been reciprocal and that the NLW may have some of these on their lists. However, my experience in family history tells me never to assume anything :)
Once again thanks for your help, it is much appreciated.