Although a bit 'far out', one of the defs of WELL in C.O.D is "an enclosed space in the middle of a building" ; one might say (altho I would hesitate) "it's inside out (out being the outside of the building) ???.
Thanks for these contributions: I suspect your suggestions are right: just inelegantly set clues in my humble opinion... but then I am used to the Daily Mail throwing in the odd archaic usage so am not too suprised!