I have just added this to the map of places to fly your drone at Drone Scene - Location # 570
Land owner permission not required.
Limted parking near to the spillway itself.
Area can get quite popular as Brecon Mountain Railway runs nearby. Also, water sports are popular on the reservoir itself.
The originator declared that this location was not in a flight restriction zone at the time of being flown. It remains the responsibility of any pilot to check for any changes before flying the same location.