I'm on the same trail so, have now got Great Grandmothers names having found Great Grand mothers names via siblings of my grand parents who had names that weren't too common, got one result for my grandmothers birth cert but couldn't say for certain that it was hers due to the address on it, but got her sisters who had the right date of birth on it, right father, mothers name was Catherine, on my GMs one it was kate, so it's a safe bet I think anyway, addresses were different but apparently it was very common to move around a lot at that time due to the size of the houses and the increasing sizes of families....
Same with my GF he's an O Sullivan, but it turns out his Mother was an O Sullivan who married an O Sullivan so its made it easier because now I can start on the Census, a lot of our GGP's seemed to get married in and around 1911 so it's hard to place them once again, one set of my husbands GGP's got married on the 9th March 1911, but it wasn't registered until the July, and both appear on the Census as living with their families.
The best bit of Info we got was the addresses on the birth certs it makes it easier to confirm things!!
Just need to get the time now to work on the next stage, great fun though and a great history lesson!!