So, some actual, discernible, progress. Ok, so the building in question hasn't got as far as cutting plastic, but the dairy (that's mostly off scene) needs to be hinted at. The concept is that this dairy was independent, acquired by United Dairies and expanded - not a stretch, it's a pretty common account - and that allows 'small' dairy/creamery buildings rather than the really quite large structures commonly seen and occasionally modelled. It's quite a small space so half-relief is the order of the day, and as noted, most of it is off set.
So, this is the churn intake building, in part modelled on a mirror image of this one, at Glynde, in Sussex, a small, independent, creamery. Picture borrowed from Google StreetView.
StreetView also allows you to scale, which resulted in this sketch (which sense checks well, with nice rounded Imperial dimensions), with a bit of assistance from a prop I made earlier:
The idea is that the deck of the lorry should be roughly level with the platform, and here's the vehicle in question - it'll be swapped around with a big United Dairies Scammell:
The end wall is a bit more pragmatic, it just has to fit... Whether I follow the canopy of the prototype, dagger boards and all, or do something different, I'm not sure.
More when I've found the plastic sheet!
Adam