Kefir grains

I began making kefir at home last November. These are some of the largest grains just before I gave them to the dogs. The grains are growing about 5% every day so I  give the surplus to them.
Is kefir useful? Yes, it is. 
It is also easy to make. The only problem is getting hold of live grains, which as far as I can see is difficult in UK. Beware of commercial  #$x?*! all about money and useless.