Thanks for the reply.
I get that responsive will adjust the number of images so that if the screen width is less then they will overflow to a lower row.
I am trying to work out how if there are only 3 images how to have them centered on the screen when the screen is wider than the images.
If I remove one of the images from the code when I run it, I get the images from the left leaving a large space at the right. It would look better if they were centered with equal space left and right.