Yes, the problem has been traced down to 1 of our Azure payments failing to process. It wasn't caused by any underlying elastic tech problems which is certainly good to know.
However, it's been a tricky process to track down. There is no information available to the end user about what the issue could be. I'm very new to Elastic and cloud services in general, but I had a colleague (who's very experienced with elastic, albeit self hosting) look through and they couldn't see anything either. It's quite strange for services to fire up and run correctly for a period of time before shutting themselves down again. I personally went through every page of the deployment and account settings and saw nothing.
Added to which I would expect that the first layer of support would have the account information that showed what the problem was and could have notified us quickly after the ticket was picked up. I'm also still unable to upgrade my account to platinum with the same error messages as mentioned above.
That said, Azure was no more helpful. I am in the azure portal every day multiple times without fail and there was no alert or indication at all that a payment hadn't gone through. Added to which none of our azure services had experienced any interruption so I was blissfully ignorant that anything was wrong that side. You have to drill right down into the billing section to see anything's wrong which is not something I was generally doing (I don't pay the bills personally!).
Anyway, all's well that ends well and I have added a bunch of stuff to my processes and regular service status checking so this sort of thing can't happen again.