First chance I've had to report back.
Sadly three more died overnight and we are left with just the one.
It's the intrepid exporer, the feisty one, the one that was guzzling food and water, and the one that took us the longest to fish out from the cattle grid as it was running around.
All the others were more lethargic, easy to catch (they just sat there), and weren't interested in the food and water.
We think that they were just down there too long in the cold and wet, and had not eaten properly, and were weak anyway .
This one is like Tigger! Trying to bounce out of the box, and trying to peck at my hand when I reach in.
Thanks for the advice beautifulgirls. Luckily we are already doing most of what you suggest.
I've got it in a high sided cardboard box near (not too close) to the woodburner, covered with a piece of voile with a fireguard mesh on top. The box is lined with an old towel, and the water is in a shallow bowl with a rock in the middle so that it can't get in completely. (It seems to like sitting on the rock ).
I'm feeding it finely grated egg (the white looks like little worms), finely shredded grass and lettuce, and a small amount of wheat bran. I've also put in a small amount of grit. (Using jam jar lids for the food so it doesn't get too messy)
I've put in a couple of small sods of earth and grass that it seems to like pecking at, and there is a warm wheat pad covered with old t-shirts cut up.
I tried the mop, but it is trying to use it to climb out with, so will wait until later when I bed it down for the night and shut the lid before I put it in.
Is there any other advice? I'm hoping that having got through the first 24 hrs it will be okay.
I'm just a little worried about it getting cold, as it is on it's own now. The wheat pads don't retain the heat for that long. The burner will be on overnight, banked down so it will not be very cold in the room, and I'll suspend the mop for it to snuggle in.
Sorry for such a long post, but I'm trying to do my best for the little fella .