Pete
Having just stumbled upon your topic when searching Google for more images of Ilkley Station, I applaud you for actually getting something built. I have been planning (though not in any major way) a layout featuring Ilkley station in its entirety for about thirty years now, and all I have got to show for it is a large shed and a lot of CAD drawings.
However, soon is the time for action, so when I saw that you were using the shed as inspiration I thought it best to have a closer look to see what others have achieved during my abstinence.
I shall be working in EM, and like you have considered the Metal Smith Cowan & Sheldon turntable. I wrote most of the Ilkley station Wiki article that you referred to!
I've amassed a heap of data and photos over the years since I first considered modelling Ilkley when I was about thirteen. You needn't bother with the Dec 76 RM. It doesn't feature a lot of detail on the shed area. I was interested in the track plan that was glued to the underside of your lid though, as it appeared to be a little different from mine. Where did you get that from?
The Scalescenes shed would be a good start, but if you are looking for anything more than a passing similarity, you'll definitely need to go from scratch. I looked at this as a 'starter' as well! My modelling period is 70s blue, so in reality the shed had long gone, but my whole layout idea is a bit of a "might have been" and so in my world, the shed was closed, but not demolished, and has been revitalised by some enthusisasts who are busy operating one or two steam engines out of it (think Carnforth, or a little closer to home, Embsay). Meanwhile the 101s, 108s and 110s rattle past in a cloud of blue smoke...
I'm based in New Zealand, so it is a bit hard doing ground-based research, but I've found Network Rail are pretty forthcoming with their archived drawings.
Anyway - good luck with yours and I may have something more than empty space to report myself one day.
Cheers
Andrew