There were a few old graveyards in the town of Neath. One being Maes yr haf. The church is still there, and if you look on Google maps, you will see it's behind Happy Homes Furniture shop., near Neath train station. In the late 1960s or early 1970s they removed most of the graves to build a supermarket...Liptons, I think. The bones and stones were removed to the new Llantwit cemetery at this time. So, when your say your ancestor was "buried in Neath" there's a good chance it could have been in Maes yr haf.