Norfolk Invasion

Can anyone out there help with this? We found it in the grounds of Bayfield Hall in Norfolk yesterday. It looks very much like it was specially forged and welded together for Unmitigated England, but when I enquired in the stables it was looked at in great mystification as if seen for the first time. Which may of course be the case; that opening could so easily have seen the recent evacuation of an alien crew. 

And then we tipped-up at Cley-next-the-Sea down the road and lo! there was an exact copy perched up on the embanking between the salt marsh and beach. This is when the first inkling of their purpose came to me. Could they be fish smokeries? The Cley example was very conveniently placed by where the catches are landed, and this would be about as fresh as a smoked herring could possibly get. But this far from the comforts of the village? Maybe the pungent smoke was a problem, but I doubt it, particularly at the assumed time of its utility. Of course it would be now, the part time residents hastily switching on the Vent Axia's in Farrow & Balled kitchens.

So, any ideas? Before I reach for that bit about the space craft unscrewing itself on Horsell Common in War of the Worlds. And, do you know, just as I'm typing this Jeff Wayne's music for the same comes ominously out of my wireless set. Please help.