So after moving my old hosting provider to a monthly renewal 12 months ago in preparation for moving it. I finally found a day to migrate it all over to a new provider on Saturday. I chose Mythic Beasts. A Cambridge based company that I have a few other domains hosted on and have been impressed by their plain talking sales, sensible pricing and proper technical support.
Their support pages suggests a “no downtime” workflow that involves copying their DNS entries for your new site to your existing hosting provider’s DNS record. So even though you do not know when the changes propagate through DNS servers both your existing provider and the new one’s all point to the same new server on your new provider’s site. Very straightforward.
I also discovered a cool WordPress plugin (Updraft Plus), that I’ve been using for backups for some time, has a very restore function that you can easily and quickly restore a backup to a new site. If I’d have known how easy and reliable this perhaps I would not have bothered exporting my site, and importing to a backup server. Just In Case.