I know from the couple of times they have done it to me, that it hurts too much not to move, especially when you were asleep. I'll get him to try thick socks, but I'm not sure that would stop the teeny sharp claws. I doubt he'll be up for wearing shoes to sleep, I don't think I would.
He did react though by putting them outside, so maybe I should try and pursuade him not to do that.