The Marylebone Farmers Market is a charming, village-like farmers market in the heart of Central London. It's open every Sunday from 10am - 2pm, come rain or shine! It offers a huge variety of locally sourced products, including fresh fruit, vegetables, meats and seafood, freshly baked bread and delicious cooked meals. Some of the stalls accept cards, but it is good to bring some cash here, in case.
There is not a website for this but the exact address is;
Cramer Street Car Park
Cramer Street
London, W1U 4EW
It's just a short walk from Marylebone High Street.