Buttermilk powder is normally found near powdered milk product in the grocery store. I am not sure that it is available to the general public in GB though. It may be one of those "American" products. In many parts of the States, drinking buttermilk is an old established tradition. I live in the Southwest and cannot find it at all....either fresh or powdered. I buy colloidal oatmeal powder in the pharmacy. It is often near Epson soaking salts. It is used in bath water to make a very soothing tub for rashes or chicken-pox. It is a silky, talc-like consistency. If you grind up your own oatmeal to make colloidal version it will never be as smooth as the pharmacy version and you will get some exfoliation even with the baby food version. I use colloidal oatmeal (first made into a well-blended paste with water) in my goatmilk recipes. It does tend to make the soap a little cream colored instead of really white. My husband is susceptible to skin rashes so I always put it in the goatmilk soaps I make just for him.