Mike
Re Strafford Sub Station.
If you fancy a bike ride and a walk through the woods, can I suggest you go and have a look at the old Wharncliffe Wood Sub Station? It's still there! It's a bit of a trek off the main path through the wood but the main building is there along with all the stands outside for the transformers and switchgear. I went a few years ago, took a load of photos and measured it up but I'm not sure where they are at the moment. I've got a feeling the sub station at Strafford was bigger than the one at Wharncliffe Wood but it would certainly be a good starting point.
Also, maybe not relevant to your current layout but if you are interested the Track Section Cabin still exists further down the line at Beeley Wood. It's a little bit easier to get to and makes for a decent walk for a couple of hours.
John