My thanks for the responses so far
To quantify some more detail. The site at Sinderland was located on Sinderland moss--near the Broadheath area of Altrincham and, although I classed it as an MU, I did so because in days past the term MU covered a multitude of sins for the RAF---in this case, I think it was an ammunition store / depot of some kind. Certainly the dispersal of the site would suggest as much and as far as I am aware, it was in use well into the 50's--but could be wrong here of course.
Now to Balsall. The Hangar has solid concrete sides--and most of the access to what would be an internal balcony / offices etc--is outside. With the best will in the world, it sits in a dip and could never have been an airfield--far too boggy and the trees have been there for a long time--you can just see the place on the left as you come fom Honiley in fact--and the revetments--heading into Balsall. It seems to be used for a variety of things now, but the Hangar was not a transportable type.
A friend of mine has also done a search on the "hole in the ground" sites--being shall we say "very interested" in such matters--and nothing at all.
JDK--erm, where are the bunkers you mentioned near Weston then ? I used to fly out of there in my younger days so am familiar with the area---just curious.
As I said, I am simply curious about Sinderland--but the Balsall Common site is rather interesting to say the least.
Any more info. gratefully received and my thanks once again for your responses everbody.