Hi NielE. Are you the NeilJ I mentioned? Thanks anyway for this info!
The pictures of your '06 with bumper cover off show several protrusions with holes in that might match the 10mm bolts you mentioned. I can only remove the bolt nearest the point where the bumper cover clips to the panel above. As I can't drop/swivel the cover down much at that point even with that bolt out I can't reach the nut that screws onto the lamp body, so anything else in that area is invisible to me! I can feel the lamp nut but can't get at it.
In despair I have phoned around Lexus dealers and, if the replacement can be done by an engineer with little hands, it would cost about £30. If the bumper cover needs dropping they would charge an hour's labour. That would mean £200... or that's what they said! I think I have to find out soon.
I remember the 3-minute bulb changes but owners who have always had streamlined HID lamps may never have experienced that pleasure. So much for the benefits of progress and style.