Ok, I've been experimenting.
   The multiple layers of most hair props made trying to select polygons for material zones a nightmare - a good idea, ccotwist3D, but beyond my skill and patience I'm afraid!

Thanks Pakled. I've actually been experimenting with a combination of moving the hair prop and using a magnet to tweak it, and am getting close to the effect  I'm after, using Koz's "all back" hair. What I've got at the moment won't stand a close up but works ok at a distance. (Maybe I'm too much of a perfectionist ;-).)
  May I ask how you produced your avatar? The style isn't quite what I'm after, but I would be interested to know.

"Don't make me angry. You wouldn't like me when I'm angry!"