To have a "supply side" view of helicopter acivity over London, take a look at the estimates for growth in heli-flights set out in this very professional report.  Of course, the noise nuisance issue is minimised in expressions such as "cause for concern", and "work round it" fixes in terms of re-routing flight tracks are offered.

Why, we ask, is the conventional wisdom of acceptance of non-essential services' helicopter activity going hand in hand with economic growth never questioned.  By how much would London's economy be reduced if such flights over the city (small "c") were banned?  Who's man enough to challenge the predicates?

Read it here.