Thanks all for the replies
I found this one today - it had wandered onto my little wildlife pond, so I rescued it from the water and luckily it was still alive but distinctly 'wet'.
I put it somewhere dry, then went and got my camera to make the most of it not moving around too much

!
Top view:
Face-on view:
As I say - amazing little critters, no more than 1/2 cm in size but boy, do they shift!!
Thea