No prime day deals in the UK , as far as I can see (although I did buy some kids' books on coding which happened to crop up whilst browsing for stuff unrelated to prime day; apparently, there's 20% off a lot of books, but that's the usual dubious claim).
Best deals occur throughout the year and are dependent on factors other than trendy fads. Mr. Washington mentioned some and I've spoken of others previously, here, but I should also now include listing errors and other languages ( I recently got Munster Go Home on Blu-ray as the German version, albeit with the full, original, English soundtrack; it's available in the UK and the US and the picture quality isn't too bad for an old film; search 'gespensterparty'. That's my plug for the day.)