Sorry to hear about your predicament Karen, but I can't see you getting any kind of visa at this stage.
We have excellent free health services here, and I'm sure your partner is receiving the best possible treatment for his illness. I am no medical expert, but I believe that if he is receiving treatment now, then his life is not likely to be in danger....just that he will need time to recover.
Try to be patient for the moment, and don't pin your hopes on visiting him here. The best (and cheapest) thing to do is to email the UKBA (website) and ask their advice, after giving the facts that you've presented here.
I wish you both the best of luck, and a speedy recovery for your partner.
