So what I need to do is join the verticles along the edge of each body part (neck and torso) so that they stay together when I manipulate the vertices with Shape Keys (which I've already done, so ideally I would link them without losing the SKs).
I've tried making the head a child of the body but I've probably done it wrong as it has no effect that I can see.
Edit: In short, I'm trying to fix gaps between body parts that occur when using sculpt to create shape keys. Ideally I'd fix it systemically but if that's not possible then a quick way to fix each shape key would be perfect!
Many thanks for the help!