Morning Jason. Thanks for the offer for the steps. I'm going to have a look round over the next couple of days to see what's available although I have to agree with you about etched steps. If I don't find anything I'll let you know.
I think I'm also going to be searching for some appropriate window etches. If I have to draw them up in CAD, so be it.
Plasticard seems , to me anyway, the best material for the base even though it will need bracing.
I have recently found this thread - "Anything You Can do, I Can Do Better ! Robinson and Downes. which has given me some new ideas as well.