Job Done! 
Well almost; I now have four EmonTx communicating to my emonPi via Raspberry Pi Zeros; I have recreated the Inputs & Feeds etc, just need to re-build my Dashboards and Apps now.
For future reference, I have attached a “How-To for Dummies” that I have cobbled together, in case it help others if they struggle as much as I do.
In hindsight, I found the process as fascinating as it was frustrating, but I have learnt a lot in the process. Words like sketch, Arduino, avrdude and miniterm are now familiar, even if what they do isn’t always …
2020-10-22 emonTx - Raspberry Pi Zero W.pdf (3.4 MB)
Once again, Thanks All for your patience !!!