In 2004 the number of Air Transport flights from the big 5 in London totalled just short of 1 million but if GA was added as well from all the local fields ie Elstree, Biggin,Denham, Fairoaks, Redhill, Northolt
Stapleford, Southend to name a few I cannot even hazard a guess and all those helicopter tracks which criss cross around the Heathrow 27 approach
Heathrow 467759 2 runways
Gtawick 190287 1 runway
Stansted 163947 1 runway
Luton 58487 1 runway
London City 52995 1 runway
95% of all that traffic is crammed in to 18 hours a day
G-I-B