Hotel Tango. With my background I can fully appreciate why some larger airfields do not devote space for spotters - we're playing a game; they're trying to provide a professional service and make money. That said, there are plenty of airfields where spotters are welcome to roam virtually freely and it is at such places where my wife and I are frequently to be found.
I do not think I could possibly come up with any sensible reason why an airport authority should devote space to "us".