Buntybear - I wouldn't know where to start! I had thought that dairy and gluten would be the first things to look at, and it did look like that might be the issue when I started (as she typically has cereal or toast for breakfast, often a sandwich at some point during the day etc), but she has been happily eating cheese and marmite sandwiches all week until this evening. Other than those, I'm not sure that I can think of anything that she had every day for a week (when she was complaining about tummy ache all the time) and then not again until today.
Anne - they haven't really done any sort of investigation, as it is all so vague. It comes and goes, and doesn't really stop her getting on with things, so I don't think they think it warrants any further looking at. What are the symptoms of grumbling appendix?
Km - I don't think she is constipated, although I wouldn't necessarily know as she is pretty independent on that front. Certainly she was pooing often enough in the week when her tummy was sore every day that I basically ruled that out as an option.