Thank you for your help on this, I think I am making progress but am not there 100% just yet.
I have created three recordsets, one for each version of the product, each with the unique product number as the product ID.
Then I inserted different Add to Cart buttons for each of the recordsets, including the required fields in the Bindings dialogue.
Finally I inserted a View Cart button.
Now, when I test the page on my local server and 'buy' one of each of the product versions, i.e. call on each of the Add to Cart buttons, I get the same product details for each version.
That is to say that when I 'buy' version two I get a second line entry in the Cart but the details are those of version one, in fact everything except the quantity 'purchased' is identical to version one, descrption, price etc.
The same happens when I 'buy' one or more of version three, I get the correct volume for version three but the product detals for version one.
When I look at the code it seems logical with the correct product IDs for each of the recordsets, but not at the Cart.
I am sure this is just a simple dumb error on my part but I am as baffled as ever!
I look forward to your suggestions.
Thanking you in advance.