My replacement ESP arrived and still nothing when connecting to PC. Meanwhile I ordered some Dupont cables to make the install as tidy as possible.
I had previously made sure to use a micro USB cable that does data as well as charging, by checking the cable using my Sony Reader (like a Kindle) which shows a dialog when data USB is connected and charging symbol when power only cable is used.
But, still nothing from either ESP.
So I hunted out another micro usb cable. The most heavy duty I could find. And it now works.
What is the difference between these data-capable micro USB cables I have?
Anyway, almost there with the build!