How Many
In reply to HHs original question I would venture to say "most of them". Whilst I do not expect you to take my reply at face value I can only say that having worked at MOD (once) and in NATO positions (twice) my experience is that 95% of the Brits are working hard. My rationale for this? Most of the people in MOD work for someone (at whatever level SO2, SO1, 1 star etc) who are pushing hard for their next promotion (not discussing the rights and wrongs of that here) and are therefore pushed very hard. In NATO appointmets my experience is that the majprity of work will be pushed the way of the Brits because they are "native" speakers (let's leave the Americans out of this). Thus, there is nowhere to hide even if you wanted to! Sorry if this is at odds with your view, but it is what my experience tells me.