Anyway, I've seen some of those layouts in the USA, down in their basements, and with scenery from floor to ceiling, and I wondered if I could do somehting on a much smaller scale, and follow up on the scenery in Watts' Yawzes Mine. I also thought I would try making the baseboard from foamboard, just to see if I could ...
So, the components assembled ...

A sheet of 5mm hardboard found in the back of the garage, an unused piece of extruded polystyrene insulation ditto, and a pack of 10 A0 sheets of foam board ...
A bit of cutting later produced these ...

A base cut from the hardboard, and one piece of foamboard cut in half lengthways, and 30 degree angle cut at the ends - which became ...

Top corners of the foamboard cut off and glued to the bottom, and the sheet then glued to the hardboard base - looks like it might get airborne soon ...
Hours of fun ...