Did you manage to get Margaret's birth cert yet? If not, I could look it up next time I'm in the BDM office in Dublin (where I live), if you like. Should I find it and subsequently an exact address in Rathmines, I could take a photo(s) of the house, as I live in Rathgar, which is only up the road from Rathmines! Let me know at your convenience.
Regards, Colette O'Rorke