Got to the bottom of this finally. To change the txt to 'More Info' or whatever in the default SP theme you change the txt in _item.php for the listings and for the carousel you change the txt in _homepage both are in the child theme directory. For the other themes you simply change the txt of two instances of it in the language_english.php file in /wp-content/themes/shopperpress/template_shopperpress/ and that should sort it. I did a grep search for "add to cart" and that is all it came up with. Works for me anyway.