cappuccetto
8 more street, w1 - This is an excellent and very affordable Italian restaurant in the heart of Soho.
el vergel
8 lant street, se1 - You probably would not discover this place walking along the street if you did not know it is there (I guess you would not even walk along this street). el vergel is, however, a very cool place to have your lunch sandwich or salad. It is cosy place and the staff is extraordinary nice.
hummus bros
88 wardour street, w1 - If you fancy hummus, this is the place to go. They have hummus with all imaginable toppings and it's cheap. The Holborn branch even has a discount for students.