Well, you're in the open FIR. Any traffic that is transiting E-W or vv and south of London is going to be coming your way. Squeezed between the London CTZ to the North and by the Gatwick zone to the South the only route is to roughly follow the N Downs Redhill - Dorking ridge/railway line .
This may well be used as a navigation training route too, but there will be enough Mil traffic between the various Mil sites in the area for the aircraft to be noticeable. Remember, lots of barracks and such that generate helo activity in the SW London area, plus Odiham and points west.
I get them some way to the N of London too, particularly Apaches (shooting trucks on the M1, I hope) the odd Chinook and occasional Merlin (Ooops -I typed Merkin! No offense). Same deal, I think.