I know part of it is that (from what I've been told and understand) if you the customer were to I.e. leak your data accidentally, it'd lead to the bank being reprimanded, and so one way it's managed is that only FCA registered third parties can access data. That being said, I don't really know how some third parties allow programmatic access in this case. Also having worked with Open Banking implementation, it's not as fun to use without having an intermediate API that the third party provides to you, rather than the raw OB spec 😅