Morning all, bright sunny morning. We were promised rain yesterday... never saw a drop!
On the subject of insulation....
It's not usually the pink foam but almost any builder's skip will have sizable offcuts of insulating foam , mostly about 4"(100mm) thick. Passed one this morning on way to get newspaper with enough neatly cut chunks to satisfy most model hillsides! Just ask nicely!
I kept a few pieces from when we had a small extension a couple of years ago, used some on grandson's "Thomas" layout.