Thanks again for all the links.
I think I will contact the local council again. The H&S inspectors have condemned the hangar and the gliding club have moved out. Some of the structure has deformation and cracks, hence the need to forbid usage.
Hope I've not opened a can of worms here as we (the RAF) could really use the space for other projects. I would like to see the hangar saved and put to good use but the MoD has no appetite for saving it.