I decided to fit the shelf to the fiddle yard board as my next step. Best to experiment here first before doing the same on the main board. I am generally pleased with the result. As expected, it considerably tidies up the appearance at the back of the baseboard.
I managed to conceal the operating wire for the point mechanism too. The cover is experimental - I shall do a proper job when I do the ones for the main board, in due course.
The turntable was something of an afterthought. I bought a kit a short time ago, but couldn't think where best to put it. The wide space on the new shelf is an obvious site, on reflection. The turntable revolves a bit too quickly to operate with any precision at the moment. I shall have to work out a way of slowing it down. The mounting spacers etc will be tidied up once the glue has fully set.