My local open prison believe it or not! The lags grow amazing veggies and sell them far too cheaply in their own on site farm shop. Last summer they had massive aubergines 50p each. A bag of 5-6 peppers including some interesting white and purple ones cost me ?1. Purple sprouting and curly Kale just a couple of quid per kilo. Leeks as thick as your wrist. They had fresh asparagus the other day ?2 per kg which is insanely cheap. Everythings cheaper and better quality than the supermarkets and greengrocers. They also produce their own pork and beef. A little know local gem. Sad thing is most of the people I have told don't bother with it because it's not Tesco and therefore not convenient enough.