I’ve just read this article about Freetrade that has an interesting nugget:
It’s also looking at an ‘auto-pilot’ feature which would automatically funnel money into different accounts for you and integrate with customers’ banks so they can see their investments in their banking app. “We want people to go to the Freetrade app, but if you’re looking at your savings app it would be nice to see how much you’ve invested,” says Fuller.
Emphasis mine. I’m assuming they’re working on an open API, but who knows?