This was no assassination and Osama was not unarmed.

Pow wow, even the American authorities have stated that he was unarmed at the time that he was shot.  As for whether or not he was 'hiding behind his wife', we will have to wait until the video is released to make that judgement, as there has been no official pronouncement on that.  (Have just heard that the US authorities have changed their story about his using her as a shield). She could quite as easily have thrown herself in front of him in an attempt to protect him: it happens often enough around the world.

If it wasn't an assassination, it was a non-judicial killing of some sort which necessarily requires some sort of debate and investigation.

I thought the mother country was with us on this

I think that we have to remember that 'the mother country', just like the US and the rest of the West is ambivalent over the real need for this action.  It's timing is convenient - early in the run-up to the mid-term elections; just after the Royal Wedding (which has captured the American psyche big-time); ... .  Will it actually reduce the threat from Al-Quaeda?  I doubt it.  Will it heighten the threat?  Again, I doubt it.  In other words, just what does the killing of BL actually achieve in the overall picture of global security and terrorist threat?  Not a lot, I'd suggest.