but can't for the life of me work out why its not doing what I want.
It would help with a better description of what you want.
There is a difference between a button being pressed and a button being pressed for a second time. You don't seem to be making that distinction on your code, do you need to?
What you want to think of is transitions, to detect a button pressed and button released. I think the just pressed is giving you the wrong thing to think about. It is that you need to detect and use that to trigger what you want to do.