Andrew hang in there, I know how you are feeling at the moment. I've been in your situation in the last few months, and watching a family member extremely critically ill and in intensive care after very major surgery, is very hard to cope with. Support your Mum, as she'll be feeling the strain big time, as you all will be, stick together, it makes it a bit easier. Keep as positive and upbeat as you can as it will help your Dad too.
The human spirit is surprisingly strong. I know everyone here is thinking of you guys and your Dad.
Sending lots of positive thought over to the UK for your Dad.