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

https://www.emergbook.win/when-choosing-a-uk-casino-with-many-high-rtp-slots-check-the-size-of-the-game

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