Diagnosed ADHD and hyperactive dude here.
Multitasking is a skill which deminishes with age (by exoerience). What you are refering to is information overload - you are not providing feed to your brain but draining your lifetime.
Imho this is due to bad habits not ADHD. You are still capable of restricting your attention to more sustainable things. Or to things others may benefit from. To me it is egoistic..!
https://www.aquamaniac.de/rdm/
Gives you an adapter and an standalone tool. All banks should use the same API, apparently.
Maybe you can use some German bank. They allow one to interact with their API for free. I use GNU cash for it. Though I doubt that you can file your taxes via GNU cash and be aligned with current UK law. You would need to check it for your own.