Hi Tony, I took a group of Air Cadets to Hendon a couple of weeks ago, in some areas the lighting was low but only for effect. No problem taking photos. It was a great day out only spoiled because it is free to get in! The consequence of being free is that local mums treat it as a crech during school holidays-of course that's when the cadets are available to go.
One of the staff members told us that sometimes she's actually treated as a childminder-stopping kids from climbing over the exibits while their mums natter away, not caring what their kids are up to.
It's a bit strange the museum over there not allowing photos, though. Of course the Vampire isn't an Air Corps one though, is it!