You can promote it, but you're very, very limited with what you can do with it.
The actual address for your store is
www.lycoseshop.co.uk/epages/luk.sf/?ObjectPath=/shops/naturallysimple.co.uk and not www.natuallysimply.co.uk
If you view both pages in your browser and select "view/source" from your browser's menu, you will see the difference. Lycos won't tell you the inadequacies of their system because if they did, no one would ever use them.
If you want a store that you can promote properly then I'd suggest acquiring real hosting and installing a fully featured shopping cart. You can acquire suitable hosting for a shopping cart from about £50/yr and you have several choices of software to use for the store, many of which are 100% free.
You can go down the free open source route and use something such as ZenCart (most of the members on here use this software) which despite being free is a lot more powerful than a Lycos store, or you can use a commercial package such as OpenMindCommerce which is a made for UK shopping cart system, see the link in OpenMind's (Phil) forum posts sig or click the banner that appears on the top RHS of this forum.
Whichever of the above paths you take, you will be far better off than staying with your current Lycos store.
These are the current details of your domain and hosting
http://whois.domaintools.com/naturallysimple.co.uk