When choosing a UK casino with many high RTP slots, start by exploring the game...

https://super-wiki.win/index.php/If_I_Want_High_RTP_Options,_Should_I_Pick_a_Casino_with_Hundreds_or_Thousands_of_Games%3F

When choosing a UK casino with many high RTP slots, start by exploring the game library size and trusted software providers. RTP shows the theoretical return, so it doesn’t guarantee wins