Phew!
Well, I got an appointment at 9.10 and took her. Told him what the last vet told me about how soon they'd be born, and he looked a bit confused and said they can't tell exactly when a cat's due, but it's unusual to be so out with the estimation.
He checked her temperature, heart, and gums and said all was normal. Listened to her belly, and I said I'd felt the kittens move, he asked how recently and I told him yesterday.
I nearly dropped because he said he'd give her a scan. He had to shave a little patch on her tummy and we went into the scanning room.
All's fine! All the kittens are alive and appear to be perfectly healthy. I saw all the heartbeats and them moving on the screen. He said there's a large number for a cat of her size, but he couldn't say an exact number because the way the scan is he could count the same one twice and get it wrong.
He said it's quite normal for them to lose their appetite a bit, and vomit little bits in those last few days because there's no room in there.
And finally, he said there's no cause for concern with her, colour, temperature and heart is all normal, kittens are fine. So I asked him again when to expect them. He said he didn't want to panic me but it's imminent now. Anytime in the next couple of days.
I feel soooo much better now.
Oh, also, I asked him if he thought she'd have any trouble with birthing and he said it's very rare for a cat to have problems. He's been a vet for 9 years and has only performed 2 caesareans.
Thanks so much for your good wishes, everyone