The delay button is between your physical and magic armour right under your available AP when in combat. You can't use it if you've acted in any way that turn, even moving for 0 AP.
I'm surprised some of you don't know where it is.
So it is, thanks.
It used to have a separate button next to flee combat IIRC which was more obvious.
On the subject of buttons I can't find, where do you hover to get the pop-up box saying what percentage you are to the next level?