Small photos stuck in the middle of the photo page for printing

That’s odd. When you deselect Centre like you said, it should let you change the printing position in two ways, as shown in the demo below: 

You should be able to change the Top and Left values by typing new numbers or pressing the up arrow/down arrow keys.

In the print preview area on the left, you should be able to use the mouse to drag where the image is on the page. (And also resize it on the page by dragging the corner handles, although I didn’t show that.)

If none of that is working, the only thing I can think of is to look at the Scale to Fit Media option, and make sure that is not selected. Because if the image is scaled to fit the media, of course it will be as large as the print area and unable to move because it’s already up against the edges of the print area. 

Does what you see look different then what’s shown below? (Of course, ignore the fact that it’s a Mac printing to an Epson printer, because the Position and Size options should work the same on a Windows computer printing to a Canon printer. I also have a Canon printer and it does work the same way, but that wasn’t shown.)