The brook is the Afon Clywedog. I've fished there many a time when I lived in GB. One of the best brooks in the area if you ask me.
As I don't live there anymore, I can spill the beans.....
I've fished pretty much most places along it's stretch and found the best places to be:-
From A5152 to A525. Here's many pools where a parachaute doesn't go unoticed. Nice fish here too.
Area around Bersham Ironworks, both upstream and down. More weirs here. A goldhead fished both upstream and down did well here.
Hope this helps