I incorporated an omega loop in the mechanism. I mounted the omega loop and the slide switch on a plywood strut extension from the back of the baseboard. It looks odd at the moment, but the strut will provide intermediate support for a shelf I plan to install later. Everything will then look much neater.
The strut is basically a plywood sandwich with a gap for the slide switch to fit tightly into.
This configuration has been designed to enable the mechanism to be adjusted from above the layout if required - important when the layout is likely to be laid out on a table top or bench, rather than on legs.
This is the underside of the baseboard, showing the polythene tube containing the operating wire. The tube had been mainly secured in position with a generous amount of wood adhesive. The end next to the points is solidly secured with some scrap plywood. The end of the wire is bent at 90 degrees to engage with the tie bar above the baseboard.
I am using a modification of the moving sleeper tie bar idea to operate the point blades. More about this another time. After extensive testing, I am reasonably happy with this concept.
Wiring on the main baseboard has begun, but is not yet far enough advanced to record here.