Hi Ray, one step further forward - the API credentials were correct but I discovered a problem in the gateways.php file from reading another post in the forum -
I edited the webassist/ecart/checkout/credentials/gateways.php file and changed
$WA_PayPal_PayPal_API_TestMode = true;
$WA_PayPal_PayPal_API_TestMode = "true";
So now if I select Paypal and Continue, it does take me to the Paypal interface and I can input my test buyer details. However, when I confirm the purchase I'm taken to the checkout_success.php page but it's completely blank. I added error reporting and it says:
E_NOTICE Error in file �checkout_success.php� at line 100: A session had already been started - ignoring session_start()
Also, the pay by card option still isn't working - if I select that option and Continue it just reloads the page.