For BadHare who asked how my kefir-making was going: Yay! Happy grains in organic whole milk, have now had two small glasses of kefir from them (one yesterday and one today). As I've not had it before I don't know what it's supposed to taste like, but it is drinkable. I was worried my house might not be warm enough as I don't have the heating on all day, but it seems to be okay. So far so good!
Thanks also to Mikegov and others who recommended trying kefir.