Great tool! Thank you :) I'm not personally vegetarian, but I found myself looking for one recently when I was in London and found it far too difficult. Minor suggestion: I'd make the "Vegan" label say "Vegan Only" (or "Only Vegan" I guess).
Also, what qualifies as a "chain"? I notice you have The Gate on there, but they have two locations, and you only have the one at Islington (and not the one at Hammersmith).