Salva I couldn't find a fix, even after doing the suggested. I'm going to end it there. Thanks for your help. Very much appreciated
Just as a FYI:
The debug.log file contained the following:
"add_to_cart_fragments is deprecated since version 3.0.0! Use woocommerce_add_to_cart_fragments instead." - I don't think that would affect the plugin but maybe? I suspect that the error has something to do with another plugin. I performed the 'remove plugins and refresh' approach to see if it is another plugin but the error still occurs. I changed file permissions, the error still occurs.