I happened to be in the area of Portobello Market yesterday (going to a spice shop that turned out to be the size of a mini-van, run by a seriously psycho American lady......), I came across this shop with a sign that looked to be from about 1974, which read "Vegetarian Hot Food, Pizza". Peeking in the window, I saw a small cafeteria-style set of hotwarmers, and a lonely looking lady.
Went in, the two ladies I met were kind, and one told me that the restaurant had been there for a very long time! The food was absolutely wonderful. It was "buy a box" style, and I had a couple of bean dishes, a rice one, some carrot salad, and a bit of pasta.
When I left, I looked again for the name of the place, but there appeared to be none. Maybe everyone knows about them already, but I'd definitely recommend them. They're almost under the bridge by West Way, right before you get to the whole foods shop (which was where I was heading).
It reminded me so much of some little dives in Chicago (particularly the Rajun' Cajun), places that looked like they'd set up shop in about ten minutes, and could disappear in about the same amount of time, where the food is wonderful.