Monzo has an open API which you can check out here. It enables third parties to access user’s data, once they’ve been given permission, of course.
It’s not stable yet so larger companies haven’t set up their own integrations & the only integrations that have been built so far have been created by 3rd party developers (as far as I know) but once it is, anyone should be able to integrate without Monzo needing the be involved.
What types of advice / intermediary services did you have in mind?