How would you plan your approach and departure if there was strong wind? Consider all wind directions.
Personally, if I asked to use that particular site I would apply for the 5.1.c exemption as I would consider it a congested area, especially as it so close to the public showground.
Consider how you would control the public if they decided to approach the aircraft en masse from the adjacent site after you have landed and are in the process of shutting down. Or starting up? Difficult.
Can you not find permission for somewhere a little further away with more options - say a farmer's grass field?