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

https://lima-wiki.win/index.php/Why_Do_Most_UK_Casinos_Have_the_Same_Slot_Providers%3F

UK online casinos operate under strict rules set by the UK Gambling Commission to keep play fair and safe. These regulations include requirements like a minimum 96% Return to Player rate, ensuring games aren’t stacked against players