I sometimes wonder if it would not be better to return to the old system where you telephoned the site you wanted to visit, discussed your requirements and they filled in a sheet there and then. No problems. No lost bookings, unless the sheet blew out the window.
Now we have a centralised system, which is obviously overloaded because people are too lazy to pick up the phone. Some data base in an office Lord knows where gets the information, scrambles it around because a chip has blown, and the result is unhappy campers. Advance booking is a nice idea but once it gets abused then it fails.