UK online casinos operate under tight rules set by the UK Gambling Commission....

https://mega-wiki.win/index.php/What_Does_It_Mean_When_a_UK_Casino_Must_Segregate_Player_Funds%3F

UK online casinos operate under tight rules set by the UK Gambling Commission. These include limits like a 96% minimum Return to Player (RTP) on slots, making sure games pay out fairly