Leeds

Like yourself, I've only been there once. If I remember correctly, and I might not, there was only one vegetarian restaurant in the entire city, and it wasn't particularly vegan-friendly. We had a nice chat with a vegan-friendly Krishna devotee we met in the street though. Overall I didn't particularly like the city, sorry. Seemed like they've done lots of bad city planning too.
 
I recommend you do a search for Leeds on this site: http://www.happycow.net/

I already did the search for you, and it came up with 35 matches. Unfortunately, when I tried to c/p the url here, it did not work properly, and trying to open the link gets an error and no list of matches. So you'll have to do the search for Leeds yourself.

I've never been to Leeds and can't vouch for any of the listings therein. I only did a search for you.

Please note that a restaurant that is vegetarian or vegetarian friendly may be willing to veganize something for you.
 
I don't spend much time in Leeds, I'm only there for the odd gig/festival, so I don't know much about the vegan scene there. However, I went to an awesome veg cafe in Leeds - the Global Tribe cafe on Swan Street. Good food, not too expensive. http://globaltribecafe.com/