I have seen several reports of users in the UK saying that they are being redirected to the US site when selecting categories to search on the main ebay.co.uk page or search results page without using any keywords. Try avoiding searching that way; you can add keywords and search, or else choose the categories using the "Shop by category" links on the left side of the search entry field.
If possible, try erasing your ebay.com browser cookies -- that way if you are redirected again, you will be forced to sign in, making more likely you will notice.
Sign back in to the UK site here:
https://www.ebay.co.uk/
Your saved searches may work better on the UK site when searching using your own shipping address rather than a default US address on the US site.
