Rioja,
I cannot give facts and figures as I have no input to the collection of the data. That is purely a matter for the Clubs themselves. They can easily see who makes what bookings to which site, and the frequency.
I only make comment that people in the past have stated their frequent visits to sites which seem to be unavailable to others. One does wonder how this is achieved. I am sure some will state it is merely a matter of preparation and determination.
The weekend issue is another matter which is possibly even more of a problem, but is probably unsolvable. I do agree there is nothing more frustrating than to decide to visit an area, which may be distant from home, only to be told you are 'unwanted' for Saturday so locals can enjoy their short break. We have experienced it on occasions. Planning so far ahead as to mitigate that issue is not always a realistic option, especially from 250 miles away as is the case of York. Booking from 10 miles or so down the road is obviously a much simpler thing to do with little commitment, and also not to do as the whim takes.
Again, it will be up to the Clubs to decide what action, if any to take. They may decide that as long as pitches are filled, and they get revenues, then they will not care if that leads to others being disappointed. Alternatively they may feel that the opportunites offered on all their sites should be made available to as wide an audience as possible. The deposit scheme has advantages and disadvantages but it does appear to work quite well for the C&CC so it will remain to be seen if the CC decide to follow suit.
Not my decision, and fortunately not really relevant to me as i now spend almost 100% of my time in the van outside the UK. Having been 'burned' I made other arrangements, but I also fully admit that the weather and lifestyle are also major influencing factors to hibernating in the Med.