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

https://research-wiki.win/index.php/Is_1,200_Slots_from_Big_Studios_Better_Than_4,000_Random_Ones%3F

A UKGC licence is the baseline, not a guarantee of a smooth experience. Check whether each slot’s RTP is easy to find, how clearly the site explains withdrawal times and verification, and whether support can help when payments stall