I visit St Catwg's regularly, as most of my family is buried there, I'll look out for your gravestone. The burial registers for 1900 onwards are kept in the church, and you can arrange a visit to check these by contacting the vicarage in Cadoxton, if the burials you want to check are before this, they are at both Neath Archives, and West Glam Archives.
Last summer there were volunteers transcribing the inscriptions on the gravestones to put onto a website, but they did say it would be some time before it's available - I would think there'll be a great deal of demand for this!
Hope this helps,
Christine