I'll be closing my account at any casino asking me for that sort of information too.
I'll bet that casinos are going to use this as a data gathering exercise rather than what its intended. I would be asking them why they are asking, if its under the AML's or responsible gaming. I certainly wouldn't think a net loss of around £100 should trigger either.
I also think casinos will lie and say they can't tell you when they can. Already MrWild has implied as such, and Dan from VS refuses point blank to answer any questions on Proof of Fund requests, manages to say its against the law for him to, but doesn't say which law when asked.
The details these are asking you for for this amount of deposits is ridiculous. If Betsafe think £500 in a month is high then they obviously only have extremely low rollers, its not even £20 a day.
Would love to know at which point these documents were asked for, on deposit (as it should be if its AML), randomly, or on withdrawal (which it certainly shouldn't be on any of the reasons).