Quite often see them in the trees around Limehouse and Canary Wharf now. They are all over the North Downs around Dorking too. Definitely spreading from what I think was their original base around Hampton Court.
Literally thousands of them in SW London........and they are spreading a bit, I saw on near Canary Wharf last week. My relatives in Hinchley Wood get them on their garden bird feeders all the time.