I'm aware that using Stripe Connect in the fully custom mode requires a lot more work from my end, but I'm confident I can handle the programming. The question is what UK laws apply to companies processing payments? PCI-DSS and GDPR are two that spring to mind but are there any others I am ignorant of that I need to follow? This will be an international site. I want to use Stripe Connect in custom mode because I want a 100% customised version for my site, which I can't get with the easier options.