Agree completely with Chill that the way the UK establishes and uses airspace is unusual - maybe even unique - and is widely misunderstood by many pilots and controllers alike. The fundamental problem is a lack of understanding of what the pilot will get from the controller in any class of airspace (and what other traffic might be encountered). If a pilot wants to be separated from other aircraft in the UK the sedret is to stick to Class A airspace. Unlike many other countries, in the UK just because you are talking to a controller it does not mean that all other IFR aircraft in the airspace will be! Having had many a long chat with pilots, many it seems are not aware of what "leaving controlled airspace, under radar advisory service means". This is not helped by the fact that the phraseology etc. used by the controller does not change much.