Something, somewhere near Brunton

I am surprised that it is on high ground falling around the perimeter. Seems not to have sufficient safety trace for flat trajectory tank shells. Although not prominent in satellite view, the is a long 'embankment' shown on OS.

Yes, that aspect surprised me too, Peter. There is always the matter of 'expedient' to consider, and Stobs Camp was long-established, and in remote terrain. If the target was engaged when passing the shortest leg, there's a considerable backstop.
Extant buildings, courtesy of Geograph;

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A panoramic shot looking from the East can be found HERE.

I note that on old OS maps the buildings are marked as Settlement implying some ancient Briton anti-Roman defence. Does that hilltop have a history?

I have Camp marked on the map on the hilltop 400m NE of the range buildings. The 1:25,000 historic overlay that I use from NLS ( maps.nls.uk/geo/explore/ ) show a very large number of linear and circular earthworks in the vicinity, most probably Bronze- and Iron-Age, and I'd be interested to learn more about their history.

Camp, earthworks, settlement and tumuli various descriptions across different map ages.