p.s. Gavin, I dont know if you use the Pixologic libraries of alphas and textures? But I recommend this alpha to you. I use it in just about everything I ever do in ZBrush, especially great for wrinkles, such as at the corners of eyes, or around the armpit, elbows, knees e.t.c.
Unzip and stick it in the alphas folder in the start up folder of your ZBrush program files (proper instructions are at the Pixologic Download Center. )
Or just say thanks, smile and ignore me... ha