UK online casinos operate under tight rules from the UK Gambling Commission...

https://www.bookmark-step.win/uk-online-casinos-operate-under-tight-rules-set-by-the-uk-gambling-commission

UK online casinos operate under tight rules from the UK Gambling Commission that shape how they manage deposits, payouts, and game fairness. For example, many games offer an average return to player (RTP) around 96 percent