I’m getting there - and I’ll write it up for the docs when I am done. I raised a similar issue before I discovered 
EmonHub Install - different instructions
@TrystanLea - you are right. I already had pip installed but I installed serial and configobj via pip as well as paho-mqtt. I’m not familiar enough with the process to understand the difference between installing via apt-get or pip.
I also rewrote the emonhub.service file based on the work by @Greebo for service-runner as well as modifying the install method.
Finally I amended my ‘emonhub.conf’ file in line with emonhub/emonhub.conf at emon-pi · openenergymonitor/emonhub · GitHub - I am not sure I have that quite right though as I do not use the mqtt interface, just the HTTP one and the emonth setup seemed completely different.
I still get the error I posted above but I realised overnight that I seem to remember there is a need to disable the serial console and I also did not check the name of the serial port.
@Paul can you remind me if I am right about the serial console and how to check which is the right serial port please?