Members/non-members

We are trying to book to stay at Brighton site on the 23rd and 24th May (Bank Holiday weekend) as our son is in two bands and has his first gigs on this weekend.  We have been able to book the Friday and Monday but not the Saturday and Sunday.  I note the site allows non-members and I wonder how many are booked in depriving me a member of the opportunity?  Why have a club and allow non-members to book on a site which appears to be full most weekends and no doubt through school holidays. Frustrating!!!!!!!!