Just to consolidate Steve and Norman's answers, here's the official website which explains everything about the Congestion Charge: http://www.cclondon.com/
just looked at that map. Gonna have to find a different route to Earls Court now. I thought I'd get away with it, with Earls Court Road, Holland Road etc being Western Boundary.
Looks like I'm going to have to carry on down Wood lane and round Shephards Bush Green :-(