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

https://bravo-wiki.win/index.php/What_Should_I_Look_at_Besides_RTP_When_Picking_a_Casino_Site%3F

When choosing a UK casino with many high RTP slots, start by checking the game library size and the software providers included. RTP is a theoretical number showing average returns over time, not a guarantee