So DP - you can see that there seems to be some ambiguity to the FIS. Welcome to aviation!
IO540
There is traffic potentially anywhere, and the UK is fairly busy GA-wise. This is why I find it bizzare issuing notams on military traffic in such and such area - they can be anywhere anyway! And they can and do look after themselves. There is no meaningful avoidance which a GA plane can do against a 500kt jet - especially as a target on a genuine collision course will be a stationary point in the sky and will not be seen until too late. The jet has his own radar.
Maybe they do have their own radar, but they don't use it to avoid other non participating traffic. There are plenty of airprox's and mid airs that show they don't. (I'm thinking of Jaguar and gliders on the Welsh Borders, a 152 and Tornado near Retford, Tornado and Super Puma over the North Sea, Tornado and Jet Ranger in the Lakes....). The NOTAMs are there to keep us out so that they can play without(?) fear of meeting GA traffic.