Have decided to post before reading Pruni's link - then will read it and see if I agree. We tried it for about ten days and it made no difference whatsoever and just reverted to nomal milk. Anyway, a few weeks later, ds2 has started to pretty much sleep through (from waking several times a night). I have no idea why at all, and he's also started to play in his cot in the mornings when he first wakes (6ish), rather than just immediately crying until we lift him. We leave him, and only lift him if he starts to cry now and usually he settles himself back to sleep for another hour or so. I really don't know why he's suddenly changed his behaviour, but I do know that our life has changed for the better due to finally getting some much needed sleep. So maybe it is a co-incidence. However, I'd have bought anything if I thought it'd work. I guess the only way you'll know is to try ordinary milk again and see what happens - if you can bear to take the risk.
Right - off to read the link.