I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission not required.
Park either at Bewl Water Car Park, for about £8 per day, or Rosemary Lane for free, can walk around the whole reservoir, approx 15 miles.
Some great shots flying over the reservoir with water sports too and surrounding countryside seems to be ok to fly as well,
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 01/03/2021. It remains the responsibility of any pilot to check for any changes before flying at the same location.