It would seem that, because of the method I had to use to download the firmware, I am stuck with the 2.0 branch, whereas many of the examples only seem to work with 3.0.
Just to recap, because the PSF-A85 module uses a 26MHz crystal rather than a 40MHz crystal, the native download speed is 74880 bauds, rather than 115200 bauds. This is why I couldn't use the suggested Flasher program.
Using the NodeMCU flasher allowed a successful download, but for that I needed to access the correct .bin file. The file I used had the path and name: Build\1M\ESP8266Basic.cpp.bin which gives no clue as to whether it is the 2.0 or 3.0 branch firmware. It seems it's the 2.0 branch, as a call to version() gives the result ESP Basic 2.0.Alpha 24
Can somebody please point me to the correct firmware file for the 3.0 branch so that I can continue my investigation of this fascinating topic?!