Well, one of the questions that give them meaning is surely the setting! As you say, the landscape that surrounds them.

Context can not be limited to the soil around a buried artifact. If you find a bowl what is its context? The soil around it? The ring of post holes that form the house it was last used in? The enclosure the house was built inside? The field system around the enclosure? The valley that the fields are in? The mountain range that the valley is part of?

Who says where it ends?

Well Tarmac, it seems. They appear to wish to say that the position of artifacts can be used to delineate the boundaries of Thornborough (on the basis of a partial search, to boot). There HAS to be more to it than that. For monuments of such size and importance we have to assume a wider sphere of influence than that, and reserve a further outer area for future techniques to explore, surely? I wonder if, in pinning all their hopes on being able to quarry everywhere where there's no immediate evidence of nationally important archaeology they've painted themselves into a corner and forgotten to leave a "generosity zone".

And THAT's before they're tackled on the basis that setting is a visual thing. The view of the henges from the whole of Ladybridge is/was homogenous presumably. How can they justify quarrying part if that's put to them?