Just to close the loop on this, I created a support ticket and Ray provided advice to resolve the problem 🙂
The station names issue (and the reboot loop that my OS got into) were both solved by re-flashing the processor via USB. The instructions I followed are hiding at the bottom of the OS 3.0 firmware update page: https://openthings.freshdesk.com/support/solutions/articles/5000832310
I gather that the USB port is only available/accessible on the earlier OS3 boards with the clear acrylic enclosure, not on the later models in the white plastic enclosure.