BHX, I hope you've got an answer to the question you were asking but just to be completely clear, if you are IFR and talking to ATC and get cleared for a visual approach you are still IFR. End of story. Class of airspace is irrelevant.
What you get from the controller in terms of separation is affected by airspace, but that's a dfferent issue. And I'm afraid I can't help thinking that notdave is being a bit confusing by his comments. The practice that is described is to do with collision avoidance and controlling the orderly flow of air traffic rather than anything specifically to do with IFR.