One thing that needs to be remembered is that Class E is Controlled Airspace and therefore VFR flights in contact are provided with a control service.
We as controllers will pass traffic information on all known traffic and anything else we see on the radar the duty of separation from ALL traffic rests with the pilot of the aircraft.
In Class G airspace a Flight Information Service is the best a VFR pilot in contact with ATC can expect and again we will pass traffic information on all known traffic (if no radar is available) or all observed traffic (if radar is available).
Again responsibility for separation rests with the pilot of a VFR or IFR aircraft (if the latter is receiving anything other than a Radar Advisory Service in the UK)