Hi, great to hear from you. I haven't looked at your tree as yet, but most certainly will. I am in complete and total agreement with you that Bridget's maiden-name was GALLAGHER. Reading my post back I can see where it may have looked otherwise, the paragraph below is a little misleading (it was clear in my head!) I have inserted (BOLD text hopefully) the clarifications that should have been in there.
". . . John McCARTHY (born Longford, Ireland) & Bridget NEE Gallagher (born Dublin) were married in Dublin (on the 22nd (or 24th) January 1860 according to birth registrations of two of their children). A few months later, like many others, they left Ireland bound for the Cape. Bridget was already pregnant and Mary McCARTHYwas born (at sea) just before they reached their destination. Hugh McCARTHY would have been born at the Cape but unfortunately I have not found much trace of him in NZ - he may have died during the voyage."
The problem was that Mary McCarthy's marriage to Bartholomeo GARBOLINO appears online under the surname GALLAGHER. [1886/27 Mary GALLAGHER to Bartolomew GARBOLINO] I was trying to get across the fact that Mary Garbolino was Mary McCarthy, daughter of Bridget McCarthy nee Gallagher. The final paragraph of my post confirms Mary Garbolino's maiden-name as McCarthy via the funeral record of her son John Bartholomew (d 6 Jun 1972).
It would be great to be in touch with you. I will get on to Ancestry asap.