Hi Alison,
Thanks for the update. If you set any user-field (i,e: Country) as default. It means, this field will be attached to all users (including non-registered users) unless the user register and change it to something else.
So, actually it is not ideal to set the country as default. Because then, you can't use "Country Specific Payment method", "Country Specific Shipping Methods".. If you want to preselect "South Africa" as the default option in the registration form's country-field, then you can write a simple custom javascript function to do it.
(use selectedIndex property for raw JavaScript, or .val() for jQuery -- google it for more info)
About the missing payment methods you have.. What payments method you currently have? Which of them are missing? Make sure you don't have restriction for those missing payment options. (no country restriction, no quantity, no min price etc..).
To show the "continue shopping" button on Mobile View. Open this CSS file:
/templates/YOUR_TEMPLATE/html/com_virtuemart/assets/css/flexible.css
find and delete this line:
div.cart-view a.continue_link{display:none!important}
regards.