When choosing a UK casino with many high RTP slots, remember RTP is theoretical...

https://wiki-burner.win/index.php/Why_is_RTP_Called_%27Theoretical%27_in_Casino_Games%3F

When choosing a UK casino with many high RTP slots, remember RTP is theoretical and doesn’t guarantee wins. Check the game library size to see if there’s variety and look for well-known software providers for quality games