Caz,
If you are going to visit, I suggest you ring the Cemeteries Department in advance to see when someone might be at the office by the entrance to the Cemetery. I think they have the burial registers there, and if you know the date when your great aunt died, they should be able to tell you which lair she is buried in, point you in the right direction to find the grave, and possibly also tell you if anyone else is buried in the same lair. They were very helpful when I visited many years ago.
David.