Hi everyone, sorry for late update.
Yes it went ahead and DD is fine. To be frank, she rather enjoyed all the attention. The drawback was that she was much later going in than any of us expected, to the point where I was starting to suspect we'd be cancelled again. We were there at 11, she'd last eaten at 7h20, but she didn't go into theatre until 15h45! She did really well and was very patient. She got a bit whiny in the last hour that she was really hungry and tired, but it was nothing in the circumstances, I was so impressed with her.
All the people were absolutely lovely and the surroundings were lovely too - it's a children's hospital so it's completely geared up for them. The nurse was so lovely and put a name tag on her cuddly. The major excitement of the day was that she got to drive herself to theatre on a quadbike. It was all over v quickly, consultant came to see us within half an hour. She said afterwards that even with the magic cream, the cannula was very hurty, but thanks to brilliant diversionary tactics, although she glazed over a bit while he was doing it, she didn't howl or anything. Really impressed with her (although she was back to normal this morning, demanding a plaster and making a fuss about a tiny little cut on her hand...).
She was very dopey for a little while, but the first thing she said was to ask for something to eat! I have never seen her eat so quickly. She was totally starving. She seemed to suddenly snap out of it though after I encouraged her to get up and walk and was dancing around all over the place by the time we left though. The anaesthetist told me that children metabolise the drugs much faster than adults. And when we got home, granny had made her GF lasagne!
We have to call for results in two to three weeks, but have already changed the diet. I asked the consultant the question I opened this post with and he said that it's 90% probability or above that the biopsy will be positive after a positive blood test and with the family history. The interesting thing was that he clearly didn't see a negative biopsy as the end of the road. He seemed prepared to consider how a GF diet affected her, as he asked us if we were planning to go GF immediately and other related questions.
What a relief to get it all over and done with!