I've got to stop you right there. NATS is only an Air Traffic Service Provider. It's contracted in by the airport owner / operator to provide Air Traffic Services and that is what it does. What it does NOT do is decide who comes in and lands at any airport. Many airports these days do indeed seem to be quite anti-GA, whether it's pricing out flying clubs, charging excessive landing or handling fees, declaring 'curfew' hours to GA, or refusing to provide free landing fees for weather diversions.
[U]None of that is to do with the air traffic controllers![U]
Ultimately, if an airport says 'no light aircraft allowed' or 'you can only come in with PPR', well it's their airport and they can choose what to do. Please blame the correct people for that decision. Even if it were to be the case, having worked at several airports in my career I can tell you that I have never been involved in turning light a/c away or worrying about whatever handling fees they're going to get charged. All I do is ensure they can get in safely, separated from other traffic and delayed as little as possible. I don't really care how much you get ripped off by the airport company, and nor should I - that's between you and them.
The above applies to non-NATS units too, by the way.