I do like that 'box, Chris, but as Mike has said, the block shelf is not quite right for Cwm Bach.
Without stepping on Mikes toes, there would probably be only a single bell, which is linked to the staff machine. However, there would be signal lamp 'light out' indicators, for the advanced starter & outer home. In addition, there might be a telephone for the outer home, for rule 55.
Below the shelf, the board would possibly be adorned with indicators and plungers, etc.
However, modelling rule number 1 will always apply, and I'm sure the signalmen at Cwm Bach will will have some seedlings trays on the right hand side of the shelf. "Gettin' the runner beans ready, see..."
Just needs a cloth over a lever handle. Someone's got to keep those handles clean...
Ian