Hi Mickwood,
Sorry about your hen!
Dont worry though, at this stage the most important thing is to keep her isolated,comfortable and hydrated. Aunties recipe is brilliant (obviously) but you can also use something called "Diorylte" available from any chemists used to correct electrolyte inbalance,which would happen if she has not been drinking much. A friendly chemist I am sure would let you have a syringe as well.
Some warm mash if she will eat it would be good too mixed with a little natural yogurt.
What does her crop look like? If its empty she hasn't been eating-does she feel hot or cold? Any other symptoms?
It would be really good to find out any health problems his birds might have. I am wondering if she has something that has been dormant until the stress of moving has brought it on.
Keep an eye on her droppings a big clue to what may be going on and keep us all posted!