Guide on Open-air Markets:
Markets large and small are everywhere in London. Many neighborhoods have smaller markets that offer food, clothing, electronics, antiques, arts & crafts, or a big mix of the above. Ask at your local town hall when and where to find your local market or, follow the crowds with shopping bags and trolleys!
Farmers’ markets: There are 15 farmers’ markets across London. The idea behind this kind of market is to trade local products – farms must be within 100 miles (160km) of the M25 (ring road around London). Most Farmers’ market sell organic products. They tend to appear and disappear quickly or to move a few streets away. To locate a market near you and make a note of its trading time, visit: http://www.lfm.org.uk/markets-home/
Go to a food markets and you will immediately get the feel for the rich tapestry of London multi-cultural society. Major food markets are described in details on http://www.visitlondon.com/things-to-do/activities/shopping/market/farmers-market, each one is really worth a visit, but if you had to choose only one, Berwick Street Market would be the best bet. Located in the heart of Soho lined by sex-shops, this well stocked fruits and vegetables market also offers delicatessen and cooked food.
Each food market has its own specific identity. For example, Brixton Market SW9 is the largest Afro-Caribbean food market in Europe. Borough Market EC1 is the oldest food market in London and an award winning one, at that. It is also the largest in the city.
Borough market : http://www.boroughmarket.org.uk/ near London bridge railways has acquired the reputation of a little gem among foodies.
To bargain or not to bargain? Etiquette dicates not really, however at the end of the market, you will get a chance to grab a few deals from vendors trying to lessen their loads for the ride home.