You are registered in the UK, but you are currently on the US ebay.com discussion boards. Trying to list items while you are on the wrong site can cause all sorts of issues, so you may want to sign out here.
Clear your ebay.com cookies, and sign back in to the ebay.co.uk UK site.
If you use your browser's autocomplete to enter addresses, clear your browser history or else you will likely be sent back to the .com site by your browser.
Make sure you are not following any US ebay.com links or using any ebay.com bookmarks.
If you are trying to list on ebay.co.uk and still having problems, you may want to post on the discussion boards on that site.
eBay is reorganizing some categories, particularly in Collectibles, so if you are having problems listing in that category, make sure the category you are trying to list in still exists.
