Thank you so much for your reply. It really does mean a lot.
Pepper is still with us this morning and was moaning to come out of the dog crate when I got up. She had a drink and then started pacing up and down the door and tapping on the glass again to be let out into the garden, which I did and she seemed to enjoy it. She is back in the house again now though and still not looking very good. She is refusing to eat anything, not even her usual favourite treats (sweetcorn, grapes, mealworms etc).
I'm going to give the coxoid a chance but if she is no better once the vet reopens after the new year, I think you are right, it will be time to let her go.
I'm sorry to hear about your hen too. I had to have my ex-batt PTS in July and it broke my heart but she was 5, which my vet said was an excellent age!
I'm really hoping Pepper picks up soon... I'm going to try and get her to eat something...