Ok I have checked out a few things.
Firstly I have to say that Paypal sand box is a right mess. It is half baked. You can't confirm emails because sandbox doesn't actually send confirmation emails (problem well documented online). Because of this you can get permission to configure the PayPal sandbox properly. Testing payments get sent from customer to seller but the seller has to accept payments, which can't be done without the email being confirmed.
For a multinational that has so much money you would think that PayPal could get this right. Overall their website is a mess in terms of layout and design.
That being said I am not sure if any of the sand box issues has anything to do with anything back at the eSop side of things. The order are still in Pending. But if I change an order from Pending to shipped. It still does not remove the Add to cart and replace it with No Stock available.
I would really like to use eShop as I have already done all the css styling
I have looked at the market press plugin and it does reduce the stock as unavailable for unique items once they go into the shopping basket. The problem with this type of cart is that all the product inventory has to be created whereas I am looking for something like eShop that adds custom fields to already existing posts/pages.
Any suggestions appreciated