Thanks so much for all your replies. They have really helped. I'd be lost without you.
It did cross my mind that her throat might be a bit sore so I'm relieved to see that some of you think the same. It would fit with all her symptoms of gulping and sounding hoarse when she's purring. So maybe it's not a furball but a sore throat. Or both!! Poor baby.
I've actually got some canned pumpkin in already. Got the one that was recommended on felinecrf.org for relief from constipation. Which she might also start with again if I'm not careful. So I think I'll try her with some. Thanks Julie for recommending that. I wouldn't have thought of it otherwise.
I've not got any cat milk in Sarah. But from what I remember Fluff likes it for a couple of sips and then goes off it. I'll have a think about whether it's worth a quick sprint to the local shop. Quick because I don't want to leave her Fluffsomeness on her own too long.
It seems also from what some of you have experienced that the anaesthetic could be making her thirsty too. I feel so much better now. Sheer panic has been kept at bay
Jan I hadn't thought of a home visit. I am quite a distance from our vets so he may not come this far. It could be worth my asking him though.
She's starting to eat a little more but seems only interested in chicken which isn't ideal.
Thanks again everyone for your kindness and advice. All fusses and well wishes will be given to the little girl xxxxx