These are my favourite kind of threads. I'd add some from Sheffield but I'm really rubbish at eating at veg*an places. My bf is omni so we try to find omni places with good vegan options so we're both happy.
BUT I can think of some others...
The Porter - in Bath. Vegetarian pub (not all the drink is vegetarian, but they have a vegetarian wine list with vegan options too)
http://www.theporter.co.uk/food.ihtmlThe food is basic but cheap, it seems to vary a lot and I haven't been in a year though. For a few years it was cheap, hearty and tasty - basically great value pub grub. Last time I went it was no where near as good though, in fact it was awful. They tried to go up-market... but you just got bland, smaller portions.
Demuths - in Bath.
http://www.demuths.co.uk/about/introduction/
The complete opposite! Expensive but delicious, and one of the few proper vegetarian restaurants (as opposed to cafes) making it great for dates/celebrations/treats. Last time I went was a couple of years ago again, but I have heard good things about it since too.
The Riverside Vegetaria - Kingston
http://www.rsveg.plus.com/I like this place, it's quite traditional vegetarian food - nut roasts, curries, etc, but tasty and I REALLY recommend the Masala Dosai, which I have had a lot of! Mains are about £10 which I think is reasonable. I haven't greatly enjoyed their desserts though, but I'd still recommend as their mains are reasonably priced and very tasty, the location is also very nice - right on the side of the river.
The Greenway Cafe - Matlock
http://greenwaycafe.co.uk/food.shtmlThis place is very much what you expect from a vegetarian cafe, quite a laid-back cafe feel. The food was really tasty, MASSIVE portions, cheap and I really enjoyed it. You can order smaller or bigger portions which I really liked, and they gave us hummus and vegetables to snack on while we waited for our meal which was random but nice. My boyfriend said he had the best mushroom soup he's ever tasted also
I gotta dash now but I will add a couple more later too.....