To browse eBay in the UK using a desktop browser, sign out of ebay.com and sign in to ebay.co.uk.
Search for a general item that shows lots of results. Sort by "Distance: nearest first". Make sure your correct location appears in the upper right of the search results page. If necessary, change your country or postal code shown there.
At that point, if things are working correctly, you should be able to search and see items that ship to your UK location, and shipping calculations should appear for your UK location.
