"Gents, on your meanderings across the Air Park, one trusts that you found the pill box and the large concrete slab (which I believe was a gun placement)"
Pillbox yes, concrete slab, maybe!! Could have been a concrete apron which is clearly shown in pix of the time.
"I am also reliably informed that on a hot day you can see the outlines of the runways in the grass...."
A nice idea, but unlikely I think. There is nothing apparent in pics of the time. Anyway, it's an airFIELD, so they just took off and landed into wind, anywhere.....luxury!!
Rgds
DOC