I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
Park up at the Black Rock picnic site on the welsh side and walk towards the estuary. The location can be busy so choose you time appropriately.
There are power lines to rear/side and towards the Severn bridge.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 08/08/2020. It remains the responsibility of any pilot to check for any changes before flying at the same location.