I have been September, December, July and March. September was the best for weather and low crowds. December was horrendous for both, we went the last weekend before Christmas and it was packed and freezing. March was cold too however crowds were low. July was very hot however busy with large groups of kids on school trips, I guess because it was end of the school year. September had prefect weather with low crowds and is our choice for next year, we are not bothered about staying in the park late at night as we like to relax at the hotel in the evening.