Blood test came back normal, except for a raised white blood count which she had at her last test (over two years ago) so vet wasn't concerned about it.
Urine test was mostly okay, but apparently was very dilute (well, obviously, because of all the drinking I would have thought!). Also, she had blood in her urine. The vet said he wasn't sure if it was cause for concern or not - he took the sample with a needle so it's possible it could be from that - so he wants to discuss it with his colleague before deciding whether they need to do another test.
Her poo is getting worse - she seems to have trouble passing much and what she does pass is very soft, and last night she dropped it outside her litter box, which isn't like her at all. Vet said to try her on sensitive food for three days to see if it makes any difference, so I'll be presenting her with that exciting news for dinner later. Bet she won't eat it!