If you haven't used the above companies, are there companies you would recommend? Comments welcome on the quality of experience when contacting support.
Mine is hosted at linode.com, a service that has been very reliable since I started using it (probably circa late 2014, if I remember correctly). I have rarely needed to contact their technical support. They offer ssh access to the console of your instance in addition to a command line administration interface, alongside a Web-based interface. There is a broad selection of Linux distributions available. Also, they notify you well in advance if the instance needs to be shut down for migration to new hardware. If I remember rightly, you can schedule the down time. Reliability has been excellent. I only reboot the instance occasionally for kernel upgrades (or for larger system upgrades).