Thanks for all the replies folks, the bunker think with the round concrete top is still something of a mystery, best guess is that it is a pre war Battle HQ, I have had this also suggested to me by the pillbox study group so I went for that until I can find 100% proof elsewhere. The only reason why I doubt it as being a battle HQ is the location of it, in the trees next to the officers mess, where the cross is on this flashearth link; http://www.flashearth.com/?lat=52.874599&lon=0.663523&z=19.5&r=0&src=msl

I have Roderick McKenzies book and did see that the building was listed as a gas de-contamination block on the photograph caption, but on the plan the decontamination block is listed as being elsewhere, photographed by me here; http://www.airfields.fotopic.net/p49141919.html with the same drawing number (6224 of 1937).

Stupidly the only thing I didn’t photograph was the Squash Courts having said that I must do that, even when I was there I mentioned it – but me being me, forgot!! Oh well, another visit sometime is in order then!

Thanks again

Richard