Can add Higher Power to this list, fairly sure one of the boys I knew growing up who'd frequent the local metal skate park of doom plays guitar in them or at least, does live. I know he plays bass for Big Cheese.
There's a little scene of hardcore bands within Neath that I've noticed, since I've seen a few videos of gigs happening which is pretty cool giving it's a proper old school Welsh town, with lots of smackheads. Brilliant.