I just got back from London and was quite disappointed by the vegan restaurants.
At the end I ate vegan stuff at other restaurants, mostly Asian. What I didn't like about the vegan restaurants is that they had too many soy dishes that resembled meat or sea food while in Chinatown(Soho) I just ordered something like mushrooms and veggies on rice and Chinese greens.
I prefer to eat vegan food that resembles the food it is: a mushroom is a mushroom.
What I liked is that you can basically get vegan food almost everywhere.