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

https://astro-wiki.win/index.php/Why_Are_UK_Bonus_Terms_Forced_to_Be_So_Clear%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