I'm a former UK controller now working in Oz (still as a controller). Your pilot is right, certainly as far as the UK goes. Outside CAS (ie class G) separation may be provided as follows:
Procedural Approach - standard separation between
participating IFR aircraft
Radar - under a Radar Advisory Service (now re-named "Separation Service") standard separation between IFR a/c in receipt of RAS and all others, subject that the final responsibility for separation rests with the pilot & that due to the inability to predict what other returns may do, standard separation may not always be achieved.
MO
