Hi haven,
Auctiva can only be used to list to eBay US, eBay UK, and eBay Motors.
If you select "eBay UK" as your listing site, the currency will be displayed in pounds. Similarly, if you choose eBay US as your listing site, the currency will be displayed in dollars.
Regardless of listing site, no currencies are diaplayed on the store window but the currencies listed in your Auctiva store should be correct. Your Auctiva store can be reached by clicking the link on the bottom right of your store window.
-Mike