A quick update on this.
Wedged here against the back with Mr. Hill's signal box mock up - it's very top heavy - I'm about 90% of the way there, just a little roof furniture and down pipes etc. to do. Yes it is a shortcut of sorts in that it would have taken me forever to chop out all the window apertures and I wouldn't even have attempted all the baby arched brickwork at the top. It's not been a joy though as I'm not used to manoeuvring 2' 6" of flimsy building around. Small sheds from Wills sheet, yes, half a layout, no. I'll be glad to get it squared up and firmly stuck down. To which...
Interdepartmental shift being what it is, the slate sheet box has ended up here, via me dumping it on Dury's Gap for photos. Note to self: build a proper photo plank.