Sky,
That picture highlights all that is wrong with these random pictures, full of figures & stats.
For a start, the population of London is at least a million more than stated and not one of those four helicopters pictured within the M25 is actually based within the M25.
Before going into specifics about population numbers, which four 'London' aircraft does your picture refer to? If you look at my picture on post 108, you may notice that the four south east 'bases' actually cover, in 20 mins, a far greater area and population than the red area in the picture you are promoting. Specifically, those bases cover from Cambridge to Portsmouth and Dover to Gloucester.
(Just putting a balance on all these pictures/stats)