http://www.maa.mod.uk/linkedfiles/re...1/chapter1.pdf
Air Navigation Order
Air navigation in the UK is regulated by the Air Navigation Order (ANO), which is a statutory instrument made pursuant to the Civil Aviation Act (1982). However, the majority of the provisions of the ANO do not apply to Military Aircraft, with the notable exception of the Rules of the Air.
The MOD direct the military (via JSP550) to comply with the Rules of the Air as prescribed in the ANO except where operational/training needs dictate. In other words, military aviators are required to comply with the Rules of the Air unless a flight is specifically authorised not to comply (low flying being the best example).
Not sure of the relevance of the above but I found it interesting enough to quote.