Two sites' category images don't match dimensions

I have created a testing website for a jewellery client

http://cm.waltoncreative.com/shop/ < this displays perfectly with all the images in-proportion.
https://dawesjewellery.co.uk/shop/. < this is the new real target website where all the category photos are square!

Now I am copying everything over to the real site, the category images all come out huge and square. I can’t find any difference between the two sites. I have looked in all the settings as well as the functions.php and style.css files which are identical.

The problem seems to be that the live site isn’t creating images in the same sizes, despite being identical.

Any ideas what I am doing wrong?

Thanks