This video doesn't include Biggin Traffic but does show all the arrivals and departures for the 5 big airports and demonstrates the lack of airspace available for aircraft to climb through to the West of Biggin.
(If the link doesn't work then search 'nats 24 layers of london' in youtube.)
https://www.google.com/url?sa=t&sour...N8ZFOD4xbU2nov