Check each site's licence on the UK Gambling Commission register, then read...

https://www.animenewsnetwork.com/bbs/phpBB2/profile.php?mode=viewprofile&u=1270170

Check each site's licence on the UK Gambling Commission register, then read bonus terms: licensed operators face a 10x wagering cap. Treat headline offers sceptically, and test mobile usability and withdrawal options, fees and times before signing up.