A good point about being unable to obtain the Mil AIP on line any more - it was available until recently, but is no longer so.
If the 'hold' isn't published, how can it be avoided? Also, the abject failure of the ATCU to provide a Basic Service is highly significant.
Whoever attends the next MCASD should ask why the Mil AIP is no longer available on line and mention that this Airprox could perhaps have been avoided entirely if the GA pilot had been able to plan a route avoiding the hold.
One could, if so disposed, indulge in aerobatics over Chedworth disused aerodrome. I know that wouldn't be a terribly clever idea, but how many other GA pilots would know that?
Another point worth considering is that the 'LARS' frequency is often too busy to call for a simple zone crossing - or to advise crossing above the zone. The VHF frequency exists; however, I suspect manning constraints preclude separate controllers being used for 'LARS' and 'zone'. Brize aerodrome itself is rarely, if ever 'busy' these days; however Brize ATC frequently is.