Wasn't really sure where to put this now, but received this from Ed at IED:
Stephen,
Apologies for the delay. MOD have finally got back to me about a WW2 event at Nesscliff & have confirmed all is ok with caveat on no SS uniforms as expected. They have a date on offer of Sat/Sun June. I have a large scale event on the part of the training area in April so if you want to attend i can show you around.
Ed
Well clearly the June date is out of the window now but we could still go for a recce in April I suppose.
What have we got in mind for it? We wanted it for Hut 9 didn't we?
Dealing with the MoD sounds like it could be quite stressful, especially as they're now bringing back a shed load of troops from Germany, the bases are going to be busier than ever.
I just don't want to recce if we aren't really going to do anything there.
Yes, Hut 9. Agree on other points.
Tell him where to stick it. This talk about SS uniforms is utter bollocks and frankly, I don't want the hassle. Nesscliffe is a great site but, IED have limited access and, dealing with the MOD is not worth the bother.
When I want your opinion - I'll tell you what it is!
Well, he's been pretty decent to us so far, so I might couch my language in a more flowery way than sticking it to him. 
...but I do have my reservations given the amount of time take to even make a decision that this is something that they might want to entertain.