That's a shame !
I received another message from Australia just after I wrote to you and you are right , his family arrived a lot earlier , before the Famine .
However , I can't imagine that Prendergast is a very common name anywhere in Ireland , so there might be some sort of family connection . If the family was RC most of those parish records should have survived . And some of the Church of Ireland records still exist .
Catherine must have had quite a story - she obviously survived all the Famine years .
I recently visited the National Archives in Dublin and their resident genealogists were really helpful . I don't know whether they could help .
After contacting the man in Australia I shall now be on the lookout for Tipperary Prendergasts , so if I discover anything I'll let you know .
Good Luck