Quite agree about the viewing gallery, there should be a check before going up there. I suspect that BAA being the true avaition people they are would just close it down rather than supply security, perhaps they should open a shop up there!.
Seriously though, those of us who work there know that are huge gaps in the security, the biggest of which (and this applies to many airpiorts) is that fact that arriving and departing pax. can still mix airside. Checkout the countries of origin of some the aircraft that use T3 and it looks pretty scary if you ask me.