So the good news is a week on and the panel and board have been connected up and duly tested. Trains have run, generally in the directions they were intended to and generally without falling off, though there is one rail in the slip that needs glueing to the slide chairs as it's wandering a bit.
The only real issues were frogs wired up incorrectly to the tortoises, but that was a matter of moments to swap wires around.
I can start fettling the track and test in earnest, though I really should learn to clean everything before I expect too much. However a selection of engines have pottered around, sometimes simultaneously as I've wired for cab control on DC to start with.
With some time off over Christmas, I should be able to get this board signed off and ready to move on to the next one. The panel obviously was the key to everything and hopefully I can now make faster progress than I did last year.