Sorry John,
I'm from Swansea though have a lot of family from Neath and there is always a little bit of rivalry.
If you don't want to get lost you can follow the River Neath for miles on cycle route 46??but it's out and back or head up the Neath Valley and then back over the top of the hills through the forests.
If you get a map there is literally miles and miles of trails through the forests east of Neath
This website may give you some ideas.
Piers