If you like some nice cool beer, portuguese sweets (the once with yellow custard inside) tasty and affordable sandwiches, good strong coffee and football, at all hours. Max Snack Bar is worth checking out.
There are three branches of this South Indian Vegetarian Restaurants across London, two in the West End. They all look pretty unremarkable from the outside, the décor is pretty basic, but don't be fooled - the food is wonderful! It's incredibly cheap and the friendly staff cater for vegans and people with food intolerances really well.