Well it's been quite some time has passed but I've finally got around to finishing this up and have now released the devices on Tindie and my own personal store.
This is the latest release and represents a shift from the passthrough method to a new style of the ESP8266 extracting the data which is viewable locally but then is also possible to post this to an MQTT broker or influxdb database.
For flashing i would recommend using the application esphome-flasher which is a great tool for writing the firmware and it has a version for most OS's. It can be downloaded from Link
The firmware is available from Link
I have created a 3D printable case which is on thingiverse. It's a snug fit but once it's in there it won't shift and the RJ45 socket ends up nice and flush with the case. You can download it at the following Link