Thank you for your quick reply Jason.
That's fine about the checkout_success.php. Can you give me some more info about what I need to put in the additional page though and at what point it loads. Also will that same page clear the cart and the session as at the moment the cart still contains the products that were just purchased and if I process another transaction the original order gets overwritten in the Orders table.
I thought setting up paypal with ecart was going to be easy but it seems to be far from it. I'm sorry to be bothering you with so many questions but if there are any other posts or documentation you can point me to it would be much appreciated.
By the way I don't think I will use express checkout because I want people to be able to avail of the option to checkout without having a paypal account.