There isn't that much difference between the CAA's CAP168
http://www.caa.co.uk/docs/33/cap168.pdf
and the MAA's Manual of Aerodrome Design and Safeguarding (MADS)
http://www.maa.mod.uk/linkedfiles/regulation/mads.pdf
There are professional fire fighters, medical staff and air traffic controllers at RAF Northolt as well providing the same service as a civilian licenced airfield. I suspect the Reubens are about to lose a lot of money to legal bills! The MOD's policy of Income Generation (formally Wider Markets) is a Government backed initiative that sells of 'spare capacity' in Government owned assets - selling capacity at an airfield is exactly the same thing. Indeed, it wouldn't surprise me if it is more expensive to assure a Government Aerodrome to civilian licenced airfield in 'real money' terms.
LJ