I was able to go to Trefil Quarry for a bit of a look around. Honestly, though, I had trouble finding the filming locations. It wasn't hard to find the cliffs but they went on and on and it was only by looking at the road, that I had any idea of whether I'd found it or not.
Many thanks to pakafe for directions on how to get there! It was worth going, even if I didn't find anything.