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

https://page-wiki.win/index.php/Is_MrQ_Really_No_Wagering_on_Winnings%3F_A_Deep_Dive_into_Transparency_and_Trust_in_UK_Casinos

UK online casinos operate under tight rules set by the UK Gambling Commission to keep play fair and transparent. This includes limits like a typical 96% return to player (RTP), which means the house still profits over time