Electrics:
Add outstanding track wires.
Review required switches and check availability: Illuminated, latching, push-button section switches - 3 required and found. Point switches and knobs - 1 required. We didn't have the exact rotary switch used previously, but we found something suitable. Point knob - we had previously used guitar-tuning knobs, but there were none left so another knob was found. Uncoupling servo toggle switches - 3 required and 3 left-overs found.
We added track feed and common-return wires to the new track sections.
The new track layout was sketched on masking tape and the component positions agreed. Holes were drilled and the switches fitted.
We needed a shell for the new 20-way connector. Geoff discovered that the American company had sub-let the manufacture of the range to a company based in Kiev. Assuming a long wait, he drew and 3D printed his own shell.