Check each site's licence on the UK Gambling Commission register. Read bonus...

https://johnnysinsightfulword.evergrovio.com/posts/how-can-i-tell-when-a-betting-site-actually-launched

Check each site's licence on the UK Gambling Commission register. Read bonus terms, including any 10x wagering cap for licensed operators, and consider mobile usability and withdrawal speed. Treat headline offers sceptically.