The sixth annual survey from the RSA about WiFi adoption, found a total of 7130 access points in London compared to 6371 in New York and Paris 827.
If you're struggling to find a WiFi access point in London, you could give JiWire a go. If you're feeling really adventurous and you're a Skype user, check out JiWire for Skype. It lets you "chat with JiWire on Skype and find WiFi access anywhere in the world". Only if you have Microsoft .Net 2.0 or above though.
If all the above is TechnoJumbo to you, try installing Skype as a first move.
Let WebTwitcher know if you've successfully used any services that locate your nearest WiFi spot.