After looking at the few available options for digital download sales (CDs & singles as it happens)(including third-party sites) and after some frustration with two WP plugins that were clunky and didn't really work as advertised, I found THIS. Simple to use, options for sales pages, or shortcodes on any page, buttons or text...exactly what is necessary for digital sales!
Note: after a small hiccup - backed up by spectacular support from the developer - we discovered that Bad Behaviour plugin was blocking the PayPal IPN calls - PayPal IPs (seen in the Bad Behaviour log) and the associated payment pages on your site should be shitelisted if using this plugin.
While YMMV, PayPal IPs are: 184.108.40.206, 220.127.116.11/33
Pages are: /checkout, /purchase-confirmation, /purchase-history (all created by e-d-d plugin)