You are missing quite a few vegetarian only restaurants. There are three I thought of immediately: The Gate in Hammersmith. or that place on Drummond St near Euston station (Diwani?) Rasa in Stoke Newington. All are well known enough to have had a write up in Time Out at some point.
I find a good way of discovering more of a particular type of restaurant is to look it up on FourSquare and then take a look at the lists it appears on.
