Thank you for that clarification and for the insight into Nik Suddards' interest.
It does touch on another pet peeve that the MOD have such a large chunk of airspace, the HRA, in which to play yet they don't stay in it. No real reason why they should of course. Anyone can fly in the surrounding Class G, only when they're not operating in the HRA it might be better were they to operate in a more universally predictable manner in which case Nik Suddards might not have had the fright of his life.
I expect that if Nik Suddards has a professional need to sling a load within the HRA he or his employer will have notified and negotiated with the RAF to the extent that he will be a known obstacle.
So the issue is really with military operations and, it seems to me, therein lies the problem. I imagine the life of a fast jet pilot is quite busy so I expect yet another thing to pay attention to, 'hear and avoid', won't be enthusiastically received.
Furthermore, how is this supposed to work low level in areas with poor communications? The fast jet could be ten seconds away behind a hill and never hear a thing. Or the helicopter pilot might be so focussed on placing his underslung load at that moment when, perhaps, a call might be useful.
If this is a real and pressing concern it needs a better solution and it probably involves the conduct of military flying more than anything else.