Technically, not much magic, apart from Mortgage and Pension, OpenBanking is quite solid in the UK, and you can connect any bank account from any bank. This is now supported by many banks in the UK. You can connect all other bank accounts directly. There are apps for that, too, for a small fee.

But I suppose you mean connecting these directly based on the national insurance number, rather than relying on user consent to use OpenBanking to see them all together in one place.