Something to keep in mind here: The employees of the Bank of England are ultimately government employees. They are subjected to the pay scales dictated by bureaucrats and politicians. Of course, they can't attract the caliber of engineers that works for large commercial cloud providers, so they have to settle for programmers that didn't make the cut. And the leadership is non-technical and from the financial and gove…
From my understanding of the article, the BoE aren't concerned about their own infrastructure. They're concerned about all the major retail banks using the same cloud provider and then that provider having a major outage. Individual banks having an outage is an issue but one that can be handled. Three or four of the main banks all going down at once could be catastrophic.
I wouldn't worry too much about that. Major outages are exceedingly rare. I can't say the same for on-prem infrastructure.