Before joining, check the site on the UK Gambling Commission register and read...

https://judahsbrilliantthoughts.rivetgarden.com/posts/what-are-maximum-cashout-limits-and-where-do-sites-hide-them

Before joining, check the site on the UK Gambling Commission register and read bonus terms: licensed operators have a 10x wagering cap. Check mobile usability and withdrawal rules too; a headline offer may be less valuable than it looks.