Imogen Hartnell spent nine years on the acquiring side of card payments, most of it in merchant risk. Gambling merchants were the accounts nobody wanted and everybody had an opinion about: high chargeback ratios, a merchant category code that half the issuing banks declined on sight, and a compliance file that had to be re-papered every time an operator changed jurisdiction.
That is an unglamorous background and it is the reason this page is ordered the way it is. The question she was paid to answer for nine years was never whether a site was legal -- it was whether a given transaction would clear, and who absorbed the loss when it did not. Applied to a casino outside GamStop, that produces two questions and they are the two this page is built on: which regulator does this operator answer to, and can its cashier actually move money to a British bank account.
The habit that transferred is reading a payment grid the way she used to read a merchant application. A logo on a cashier page is a claim, not an arrangement. PayPal's near-total absence from this market gets its own heading here rather than a footnote because it is the single clearest example: the method readers ask about most is the one the operators are least able to offer, and a site advertising it is telling you something about itself.