I read a lot about people saying, UK wise, they get stressed over if they're being paid. Dont know what casino's you used to play at but if i HAD to bet my house i'd say the following will give no no issues: William hill, Bet 365, Novibet (unless SOW) Unibet and Sky - still a lot of casinos here that will not hit you with BS. Even Videoslots.
I think this is a real concern for players making high value deposits and withdrawals.
I had given a single operator almost all of my play for 6 years.
Before I called it quits, I was asked to complete SOW twice in 2 years, despite no increase in annual turnover.
They also checked a £20,000 Royal Flush AND an £8,000 Royal Flush with NetEnt, taking more than 5 days to give the 'all clear' on both occasions.
I closed my account with them (refused to complete another SOW) and played briefly with MrQ. They were great. I had three large wins with them, including a £20,000 Royal - all paid promptly but it was a worrying time wondering if that would be the case.
A perfect time to quit on a high, so I did just that. Registered with GamStop for 5 years to remove any temptation and now only play at land based casinos... who knows if SOW will be requested there in the fullness of time!