i dont live anywhere near borough market, so cant help on that front. each area will have their own - my area gets bare pikey clothes stalls and nothing else!
markets are markets....standardly, it depends on whether you know the people you are buying from to get those discounts.
for example, my chef buys fish from a market up in town (i forget which one). but as he knows the dude who runs the market, he gets the discounts. when i go up, i get bumped....
such is life though...
more london flicks are needed though!