I took it up another level of subdivision and worked on the head. It's now asymmetrical and more detailed. I've also added vein detail to the exposed areas of skin.
I've still got to refine the hands and feet at this level. I should be able to define the finger and toenails better.
The whole model now stands at 9.5 million polys which is near the limit of my laptop, so I might not be able to add another level to add skin detail and surface detail to the clothing without having to move it to the desktop.