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

https://blast-wiki.win/index.php/What_Does_%27Cost_of_Entry%27_Mean_in_the_UK_Online_Casino_Market%3F

UK online casinos operate under strict rules set by the UK Gambling Commission to protect players and ensure fair play. One example is the requirement for games to have a return-to-player percentage of at least 96%