UPDATE: SORTED - was looking at wrong table, lol
I added a site manually.
Then installed the Piwik WP plugin on my site to insert the code.
Though because I am now running a multisite install, the plugin did everything for me (excellent) and registered the site for me.
Now I have the that site twice in the Website Dashboard.
How do I delete my orginal manually created one to avoid confusion?
Many thanks.