Thank you so much for doing this Dawn!
From your description of the signature this does indeed sound like further supporting evidence although it leaves me wanting to see the entry for myself to determine whether it could possible have been "Gaston" that she crossed out.
It certainly is intriguing - if this is in fact Mary Ann Gaston, then I now need to figure out why she consciously signed as Brooks (and referenced her grandfather as her father) rather than, as I had assumed, it was a mistake by the registry office clerks. But this is what makes family history research so addictive!
Thanks again for your help, I really appreciate it.

Peter