I have just added this to the map of places to fly your drone at Drone Scene - Location # 560
Land owner permission requirements unknown.
Limited parking is available by the railway bridge just off Fontygary Road - also a layby approx 100m down provides a few more spots. Either way, a short downhill walk, throogh / over a style and wooded paths leads you to the back of teh Lime Kiln building and a pond.
Technically you are inside the Cardiff FRZ so I would call Cardiff ATC and St Athan’s ATC (if daytime) to advise so no panic sets in. I have written permission ‘in principle’ that it should be fine to fly here just pre-advise on the day to the ATC.
Also, be aware that there is quite a bit of wildlife here. If tide is out then there is a huge beach the other side of the sea wall and a short stroll takes you to Aberthaw Power Station (where more parking is also available).
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.