Hi
I was told initially that my son shouldn't fly, but when he was sent to see a specialist in ITP, that consultant said it was fine for him go on holiday with a count under 20K. He wasn't at all concerned about the plane, but did tell us to ensure that we were somewhere near a decent hospital (just in case) and that we had adequate medical insurance. We also took a letter from the hospital with us in case there were any problems - my sister translated it into spanish for us before we went. The plane journey from the UK to Spain is only about 2 1/2 hours, so not a long time in the air. My son's count seemed to plummet when we got there, so I spent most of the week worrying about being thrown in to a cell by Spanish police and questioned about the spectacular bruising he was showing, but all was fine in the end!
Hope you manage to get on your holiday and that it is as relaxing as ours was.
Ali