It appears that the main belligerents are non-Brit Long-haul Pilots who have really no conception of :-
1. How small the UK is.
2. At any one time, the large number of GA aircraft over the island.
3. A great deal of the UK is covered with CAS, a lot of it down to quite low
levels, unlike for example, the US, France and Scandinavia.
It is worth pointing out that the CAS referred to is Class A airspace reserved mainly for the CAT. It is a bit of a bummer flying around at 2300' with the Class A floor at 2500'. It is easy to get a bit unsure of position when you are swiviling that head to watch out for all the other traffic whizzing around at the same altitudes.
An American friend was surprised going along the M25 from Denham to Stapleford how close all the aircraft seemed to be. Back home he would have called them near misses.
Not the place to be doing orbits if you can help it.