@ajb2k3 No worries, your reply (and support of the forum, thank you) helped me take another step in the right direction so I appreciate it.
The thing that bothered my about the UIFlow IDE when I tried it was that I had to push code from the web every time I booted the M5Stack (is there a way to store the code for the next time it boots?). MicroPython proper allows you to upload boot.py and main.py to permanently define the behaviour of the device.
So far I have used rshell (in place of ampy, etc.) and allows me to do everything else I want (the command 'rsync . /flash' is powerful - it syncs the M5Stack's flash folder with whatever files and directories are in your local directory).
I've run M5Burner previously, to install UIFlow. I didn't run it this time - I copied what I needed from the firmware/fw.json file.