My husband and I are both veggie (as are the kids), but we're also foodies so love exploring new places and cuisines. We find that when we go to non-British places the vegetarian options are less of an afterthought.
Lebanese restaurants have amazing mezzes which fill us up.
Ethiopian is great with the injera and lentil curries.
Oriental food - Thai, Malaysian, Vietnamese
Indian - love the variety. Love paneer dishes too.
Tapas- we've been to a few tapas places recently where the evening is more about munching on small plates and drinking wine/sangria and chatting. Much prefer this than one stodgy meal.
If we do go to a more traditional restaurant it will be more to do with the ambience or the view or the live music. So then we can forgive and uninspired meal.
But a lot of places are now doing vegetarian tasting menus and some great chefs are leading the way- Jason Atherton, Pierre Gagnaire.
The issue is always when you are a lone vegetarian faced with a set menu, and then really at the mercy of unadventurous chefs. But those are the times I think that the evening is less about the food and more about the socialising. It stills pains me if I have to fork out for it though.