Payment at AS in CC site guide

We are beginners and recently spent 10 days at Wood Farm AS ite at Charmouth in Dorset which we had to pay in full, up front. The site was very good and we have no complaints about the facilities or services. However we were unlucky to stay there in late June during the mansoon season! We stuck it lot for 6 days and on the 7th decided that our home county of Kent looked drier and sunnier. I approached the site office and asked what the position was about a refund or credit if we left early 3 days early. I was told that they didn't have a policy for either! Needless to say we won't be returning. Why can't the AS sites be required to be as flexible as full CC sites with regard to payment as a condition of being in the site guide, which must bring them a lot of business?