Further to the Kefir mentioned earlier .. why not 'grow' your own Kefir. (This might benefit FBG as well)..
It will be fresher than anything you could ever purchase from the shops... and most definitely more palatable.
For a good many years I have done my own, but since recently developing a dairy intolerance, I now cant have any at all.
Just purchase a few 'Kefir milk grains' on Ebay .... 20grms will start you off. They shouldnt cost more than £3 or £4.00 .
Put them in a Pyrex jug or glass and add somewhere between half a litre or a full litre to the grains. 24 hours later pour the contents of the glass through a nylon sieve into another glass. The grains will be left in the sieve and the rich creamy drink will be in the lower glass. Then just start again, put the kefir grains back into a clean glass and top it up with milk. Simple as that .. 24 hours later you will have another drink ... do it again and again, mine lasted for years.
The kefir grains will start to multiply fairly quickly as you create more drinks. Very quickly you will have more Kefir grains than you need. Remember these are live cultures and beat all of these
pro-biotic drinks which are a bit expensive that you see advertised on TV... and yours will be live friendly bacteria unlike the few day old ones on the shelves of the supermarket.
If you don't like the taste ( a bit like plain yogurt) add a little squash to it.
Should you want to speed things up leave the glass out on your worktop, the grains will grow faster and the drink will be creamier.
Personally I preferred my drink cold, so mine stayed in the fridge.