British food is much maligned, mostly by people who still think it's 1950. Food in the UK especially in London has undergone an incredible transformation and now London boasts some exiting restaurants that reflect it's cultural diversity. If you want something casual then Borough Market and Maltby Market offer that. They have a wide range of fresh food to eat there or to take home. I am not sure there are too many places you can wander around eating freshly cleaned sea urchin, oysters and drinking a glass of sparkling wine