All of the feedback is appreciated, thanks.
My son is moving house in the next few weeks. He has a 12x8 garden shed that is very well made, water-tight and less than a year old. He is giving it to me.
At work, our bricklayers have dozens of sheets of un-used 2" and 4" high density foil backed insulation that they want shot off. I can take it anytime, free. With that in mind, I am thinking of taking the shed and re-building it with a 4" insulated base and filling the side panels with the 2" high density foam, followed by 4" foam into the roof area.
This would give me scope for a really busy layout that would keep me motivated over many years with no limit on track space.
For anyone who has a layout in a shed, is this a worthwhile option considering that Ireland spends most of it life until a shower of constant rain!