I just re read your post...just out of interest, when they said they were putting you on a "supporting attendance" thing -what did that entail? How did they support you?
It's terrible that you felt you had to refuse hospital admission. And don't feel sorry that you had to ask for help...that's what we are here for...ask anything anytime rather than worrying.
My advice to you (with my union rep hat on)would be...as I said in the last post, explain to your employer exactly how bad you feel and that you are worried about losing your job and all that entails, explain to them how debilitating the illness is(ie it's not just a dose of diarrhea), that you feel pressured into coming into work when you should have been hospitalised, and ask that instead of making you feel this way, they do what they can to alleviate stress,remove the supporting attendance thing, and relax the trigger points for you. Tell them that they will be seen as a good employer rather than the dickensian types they appear to be. Mmm...maybe don't call them dickensian at the meeting, they won't like that!! but do make out that they will be good employers if they listen.
Hope that helps -wish I could come in there with you! don't mean to tell you how to suck eggs - but a good thing to do is write down how you feel and the various points you want to make before you go in to any meeting, and don't go into a meeting alone. Get your union rep in with you and explain it all to him as well.