They definitely stay in place, and are meant to work very well for most mums, they just didn't work for me because milk leaks from a couple of spots on the areola as well as the actual nipple (yes too much info I must be a freak )
They work by applying pressure on the nipple to stop it leaking.
Thanks a lot I think I will give them ago - anything not to have to wear a bra at night which killed my back last time. I seem to remember milk coming from outside the nipple a bit too so eeek I might be a freak as well! I'll get some I think even if it is just for the odd night's break. Did you use them straight away? the website says to wait 4-6 weeks for the milk supply to be established but that is the time I would really need them I think.