Originally of clay lump construction I'd guess, dodgy bits have probably been replaced by brickjbex, otherwise it is pretty much what you would eggs pecked at the back of a Norfolk cottage.
Later discovered that one half of the shed was unmolished and the brick wall put up by the son of previous incumbent.
Just in fromt of the gable-end I suspect there wos a well, as there are loose brickses and other rubble filling in some hole or other. 
If it are, it will going to bee a well I'll be blowed. Mr. Toad will have to find an arj home.
 I'm devv^diva^divvy^dever^most unhappy to relate that there never was a well there and all the brickses and stuff were from the unmolished bit of the shed chizz rotten swizz.
Well, (dammit - thre isn't a well!) a new shed is being put there. Well, far from new, it's half a nold wooden gridge, but it's becoming a shed, and it's new to me, so there!