...also migrating AWAY from Fastmail (Australian) and TO an European provider sounds like a very bad idea - I'd kind of want both the US and the EU legally away from my coms at all costs (!)
Is it that different? Being Australia in alliances like "Five Eyes" I don't think you can keep your stuff away from the US at least when using Fastmail.
If you want both US & EU away from your data, I suppose you will have to consider things like Yandex Mail, which comes with its own set of problems too, of course :)
The problem is that, even if Fastmail are Australian, they host exclusively in the US. They state that sure, there is the possibility of interference at the data center level, but they rely on their anti-hacking measures to prevent unlawful access
If you want both US & EU away from your data, I suppose you will have to consider things like Yandex Mail, which comes with its own set of problems too, of course :)