I don't know if you remember my talking about the so-called buttermilk 'plant', but I said I would try to find more information on it and here goes. I've just had an e-mail from Tim Allen of the Ballymaloe cooking school in Ireland, and they no longer use the recipe for buttermilk as it's too unreliable. He said goat's milk or whole cow's milk has worked well in the recipe, but since our milk these days is heavily pasteurised, they don't always get good results. They now simply sour their own milk for use in their soda breads. I did try it, by the way, and ended up with the smelliest mess of rotten milk ever, so bad that we had to lean heavily on the Febreze in order to get rid of the stench.