to chip on on rodan's point...
Unregulated airspace (Class F&G... outside CAS) is an unknown traffic environment. The ATS provided in the UK in such airspace is advisory and does not guarantee separation from other traffic... although ATC will attempt to separate (Most airspace users know this... although I wonder about some of the International flights we get into our airfield that have to transit a chunk of Class G to reach us?)... It is not a perfect system, but there is massive competition/resistance to establishing more regulated airspace and restricting the "rights" of aviationists of all persuasions... and there are plans to increase the amount of "known traffic" airspace, but it's not there yet!
(Sorry if this is repeating what has already been said?)