[Facts] Re: Is Margaret a variation of Martha?
Good luck to you, Mary! I know how frustrating hunting dead ancestors can be -- especially when those ancestors used nicknames instead of their given names.
I see that you're posting from Australia, so there's not much advice I can give you, as I'm mainly familiar with U.S. Federal Census records research and stuff like that. I hope you find the pieces to your puzzle.
-- Nanaea