Can someone please tell me how to add different parts of a new mesh to one texture and map them in Milkshape using the texture co-ordinator?

Ie: Bed head, Bed foot on one texture in Milkshape.

Thanks

When creating and mapping those parts you simply map them to the same area of texture. It may be helpful to you to create a little template texture - say, put a rectangle in a solid colour on a temporary texture, import it into Milkshape, and then, with your bed head and bed foot still in separate groups and that texture applied to both groups, map each group separately to that coloured rectangle. Then, when you regroup the head and foot into a single group, they'll be in the same spot and will share that texture.