More on the turntable saga later, as mentioned in my last post. Here is a sketch of the track plan. The diorama is 186cm by 40cm.
Note that the ash plant wagons run straight across the turntable, an important consideration I think. In fact it would probably be only one wagon at a time. The coaling stage is as shown in a recently posted photo but I am considering a typical wagon-to-tender affair with water tank over as seen at Monument Lane. The wagon siding would be slightly elevated to allow hand shoveling of coal across into tenders/bunkers. A nice compact arrangement though hard on the shed staff.