Hi,
For the benefit of others, I've answered my own question with the approach that worked for me.
With the information linked below, the process should consume about 20 minutes over an elapsed time of about 2.5 hours.
The solution is a variation for Catalina based on the check-list from MacKeeper available at: https://mackeeper.com/blog/post/473-step-by-step-guide-to-reset-mac-to-factory-settings/
This list includes preparation for the clean start by running through another check-list from MacKeeper available at: https://mackeeper.com/blog/post/470-your-must-do-checklist-before-you-reset-macbook-pro/
Run through the main checklist but note that with Catalina:
- In the Disk Utility, delete the group of drives - see button in bottom-left corner of window that pops up after you click 'Erase'. This deletes 'Macintosh HD' and 'Macintosh HD - Data' then re-creates a clean 'Macintosh HD'; 'Macintosh HD - Data' is recreated when Catalina is installed; earlier versions of MacOS appear not to require 'Macintosh HD - Data'.
- Choose APFS (APple File System), rather than Mac OS Extended (Journaled) - gleaned from https://blog.macsales.com/51838-how-to-clean-install-macos-catalina/
I re-installed from the image on the macbook (via Command + R held at start-up) but was connected to the internet via ethernet LAN and had the power supply connected.
I have so much more confidence in the machine since the re-imaging. The machine was years old when I bought it and although it had been set up with Catalina, the re-imaging presented the opportunity to set the machine up how I wanted it - as described in the 'Post Install: Configuring macOS Catalina' section of https://blog.macsales.com/51838-how-to-clean-install-macos-catalina/.
All the best
Dave
