Your question

Ally -
You asked:
"BTW if my tumour was 25% HER2+ does that mean that I overexpress that gene but that only 25% of my tumour cells were taking it up? I don't really understand how it works."

This 25% Her2 business was one other thing I did not understand about your post. It seems to me that you either ARE or ARE NOT positive.
Maybe that means that you have two kinds of cancer at once, each with a different cell biology.
I am not a nurse or other professional in this regard, so would be interested in what kind of answer you can get on this.
The rest of my question is what is the "overexpressed number" of your Her-2? You can be her-2+ (which means "not really"), Her-2 ++ (which is positive). or Her-2+++ (very positive, and the number in my case). All these answers are necessary in determining how helpful Herceptin might be in your case.
Keep asking your case managers for more enlightenment, as Knowledge IS Power!