Hi Sue, most of the gravestones where moved during the 70s, they where piled high and laid out on top of each other to form the large grassed slope at Parliament street end. Some stones where used as floor flags around the cemetery and the back of the cathedral. Although i don't agree with what happened to them.The remaining stones that are scattered about the cemetery are not in there original places.
I often walk through the cemetery, if i come across the name Samuel Povah i will get back to you. Mike Faulkner who owns this site might have some information that's helpful.