Can I change the 'add to cart' button to my design, if yes, how please.
You can change it according to your design.You can use firefox firebug plugin to check the css code for the add to cart button and change it.
Many thanks
Please can I use inspect element in chrome to edit the design?
Of course you can use chrome's inspect element to check the css code,edit it to see the live result,after that change the code from the css file.