There are lots of threads on veggie food on here...do a search on 'Cauldron', which is IMO the best fake meat brand, and you will see all of the different topics.
London is great for vegetarians. There are a few fantastic veggie restaurants ('Mildreds' is by far the best) and actually I think the veggie choices in supermarkets is excellent - I have seen it growing year on year. I became veggie in 1999 when things were pretty dire, and now they are great.
I have seen boca in health food stores, and places like Planet Organic. Oooh, just had a craving for boca ravioli!
Vicky