I have used
Mals eCommerce with a lot of success. It integrates with PayPal as the gateway. It's free, and an upgrade is available to avoid sending customers to the PayPal site to finish the transaction.
You can set up discounts and vouchers and add many other features.
In many ways it works like paypal, but offers more features. You can set up your page however you want and add your own "buy now" button via a form or a simple html link.
Good luck. By now, I'm sure your head is swimming!
