But how on earth do move the cursor back to the centre of an object in order that I can create new ones from the same centre point? My example: 3 cylinders stacked one on top of another. I have inadvertently moved the cursor away from the cyclinders and now want to create another cylinder from the same centre point as the previous 3. But short of trying to click the cursor somewhere near the middle im sure there must be an easy way to put it right in the middle where it was, isn’t there??? Thanks in advance.
Not to worry. I think I have worked it out. Using the centre, centre new and centre cursor button. 
Center, Center New and Center Cursor change the location of the center, not of the cursor. If you want to move that, press Shift+S.