Fearlessly brushing aside Shelob's little cousins, I dug out a couple of leftover sheets of styrene -- 1/8" and 3 mm -- and sliced them up for walls and loading dock surface.
Having found a new online supplier for "brick" styrene sheet, I was able to clad the first wall sections ...
... and attach them to the deck with lacquer thinner and styrene angle bits for reinforcement. I shall cut the other bits of wall to fit the gaps (no Australian reference intended).
And here she be right side up and with the crane in situ.
Copying David1226's Claptowte dock, I graved paving slabs into the styrene platform surface before assembly.
The near end of the loading dock will butt up to one end of the goods shed (this 'un with the raised doorway).
I am thinking of holding shed and dock together with a magnet or two, so they can be easily separated for moving and storage.