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

https://www.save-bookmarks.win/ukgc-is-the-baseline-not-the-whole-test-check-if-rtps-are-clear-cashout

A UKGC licence is the baseline, not a guarantee of a smooth experience. Check that RTP information is easy to find, withdrawals are processed promptly, and responsible gambling tools are simple to use