I really want to get kefir into my life but I don't know where to get it!
I get mine from http://www.nourishkefir.co.uk/ but I buy it from a local health food shop.
There's a 'stockists' link on the site which shows you where you can purchase locally.
I make mine into a smoothie with a tub of bluberries, 2 tablespoons of flaxseed (from these guys: http://www.linwoodshealthfoods.com/) and a tablespoon of cashew butter - it's absolutely delicious!
Here are two people posting ads for fresh kefir grains. http://www.gumtree.com/search?q=kefir&search_location=United+Kingdom&category=all&search_scope=title