Ralph.
We have the Helilanes on our radar map. The problem is that you the route (such as H3 near teddington) is only "deemed" to be separated from 27L at LHR if you are on the route. The minute you come off it geographically or by level you may set the radar fashing red.... which means paperwork and possibly a G/A at LHR due to TCAS RA.
I have sent you a PM as I presented to RAF Odiham on the subject at the Station Flight Safety Day.
Alan