Many thanks.
Regarding your comment under #5, the product key sticker is on the back of the 'Getting Started' leaflet included in the box with the CD. The leaflet gives two ways of installing: (1) 'Installing from the website (recommended)'; and (2) 'CD installation'.The website for (1) is given as www.norton.com/setup. This site prompts for the product key prior to download, although whether it would go to an up to date version or not I don't know.
I don't know what sort of special activation arrangements retailers might have, but does this sound like one? Provided it doesn't, I'll follow your 'trial version' download route.
Peter