Hi Paul,
I like your idea to model the stabling point. Would you be inclueding the line with the step gradient as part of your backscene?
Knowing your space constraints you may like to consider my two suggestions. You have probably researched these ideas already but here goes..
First, Birkenhead Mollington Street.. the refueling point using the new part of the shed as a backscene, it also has a scrapyard behind and is set in an urban/oily/grimey industrial area. Great for showing your locos off for a photo diorama.
Second, Buxton Tmd refueling point. A nice scene to model and an excellent photo plank.
Best regards,
Steve