Only the one building, a Quadrant Tower. Originally, there would have been two, but only One survives.
It is typical of a RAF WW2 bombing range quadrant tower, they were arranged so that they could between themselves, score the accuracy of the practise bombing, usually the two quadrant towers and the target itself formed a triangle. Typical layouts from a RAF WW2 design manual are below.
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The tower, near Cockerham Sands caravan park:
The RAF Bombing Targets design manual:
Typical quadrant tower:
Targets themselves:
Floating:
Marsh Type:
Marsh type, as found on the Dee Estuary:
Typical range layout:
Typical Ground Markings: