David,
Templates seem to have passed me by! Seems like that is the best approach for what I need.
I had a brainwave, a better method using templates
If you have a set of images in the queue and want to replace one
exactly in the same position, size & crop on or off, this works, just tried it.
Save the set as a LAYOUT with a suitable name.
Clear the queue
From the Print Properties menu choose Custom-Layout and select your layout.
This will load the queue again with all the images but in a Template.
Remove the unwanted image using the red button on the image; this will leave behind a red template.
Drag the replacement image to the red template - done!
The only adjustment that may be required in the page editor is the position of any crop on the crop tab.
If you want to re-use that template with a new set of images, remove each image individually with the red button and save as a layout with a new name. Remember, to use a saved template it's Print Properties - Custom - Layout.
Terry
PS. There's a Learning Video on Templates here
http://www.youtube.com/watch_popup?v=1TjdBbj-r2E&vq=hd720