Hi ntegragsr93,
The token generation process is actually the same regardless of what eBay site you are registered with, so you can go ahead and generate your token using the "Get New Token" link on your "Ebay Settings" page.
Once you have generated your token, in order to post your listings to eBay UK, please select "United Kingdom" from the "eBay Site" pulldown menu at the upper right of the Auctiva lister page.
-Mike