If you want to complain about police helicopter operations, you could write directly to Met Commissioner Sir Bernard Hogan-Howe , New Scotland Yard, SW1.
On general helicopter noise problems I think Wandsworth Council has a Helicopter Noise Forum. Write to the Clerk, Francis de Lima. email@example.com - I know this is not local to Southwark but it is where the helicopters are heading/taking off from usually (at Battersea heliport). Might be worth cranking up some opposition from other boroughs too.