A UKGC licence is the baseline, not a guarantee of a smooth experience. Check...

https://chancessmartperspective.nexorafield.com/posts/how-to-read-a-casino-payment-policy-without-falling-asleep

A UKGC licence is the baseline, not a guarantee of a smooth experience. Check whether each game’s RTP is easy to find, how long withdrawals usually take, and whether payment conditions are clear