After much fannying around with loading 0.3 up manually (0.4 is still unfortunately broken, which is such a shame) I HAVE managed to get the plug in present within Domoticz. However, it only half loads the configuration screen. Domoticz appears to be otherwise working. Here is my log:
2017-05-02 16:43:32.808 Domoticz V3.7403 (c)2012-2017 GizMoCuz
2017-05-02 16:43:32.808 Build Hash: 78af35c, Date: 2017-04-30 16:33:55
2017-05-02 16:43:32.808 Startup Path: /home/pi/domoticz/
2017-05-02 16:43:34.032 Sunrise: 05:28:00 SunSet:20:20:00
2017-05-02 16:43:34.032 EventSystem: reset all events...
2017-05-02 16:43:34.163 PluginSystem: Started, Python version '3.5.3'.
2017-05-02 16:43:34.171 Active notification Subsystems: email, gcm, pushover (3/12)
2017-05-02 16:43:34.172 WebServer(HTTP) started on address: :: with port 8080
2017-05-02 16:43:34.178 WebServer(SSL) started on address: :: with port 443
2017-05-02 16:43:34.180 Proxymanager started.
2017-05-02 16:43:34.181 Starting shared server on: :::6144
2017-05-02 16:43:34.181 TCPServer: shared server started...
2017-05-02 16:43:34.181 RxQueue: queue worker started...
2017-05-02 16:43:36.182 Nest: Worker started...
2017-05-02 16:43:36.182 EventSystem: reset all events...
2017-05-02 16:43:36.183 EventSystem: reset all device statuses...
2017-05-02 16:43:36.184 EventSystem: Started
2017-05-02 16:43:36.534 PluginSystem: Entering work loop.
2017-05-02 16:43:38.186 Fritzbox: connected to: fritz.box:1012
You can see that Python plug-in is loaded (I upgraded to 3.5.3), and also to the latest Beta of Domoticz, so I'm now at a loss as to what's going wrong with it only "half working" - by that, I mean I can't configure it, as per the dialogue box below:
Does anyone have any idea what I can do to get this working properly...? As you can see from the box, my Domoticz build is 3.7403 and I'm running this on a Pi if that's relevant. I've tried renaming the plugin subfolder from "BroadlinkRM2" to "broadlinkRM2" as I've seen it used interchangeably with and without the initial capital letter - it doesn't seem to make any difference.
Here's the initial part of plugin.py in the plugins/broadlinkRM2 folder: it DOES seem to have the necessary parts that would (or should!) be creating the dialogue box to enter the IP address etc. But as you can see in the screen shot above, they're just not happening...

# Broadlink RM2 Python Plugin for Domoticz
#
# Dev. Platform : Win10 x64 & Py 3.5.3 x86
#
# Author: zak45, 2017
# 1.1.0: code compatible py 3.x
# 2.0.0: import from e-Control or any other ini file with similar structure
# webserver for file transfer
# Off action managed for generated devices
# clean action to erase files from import folder
# Below is what will be displayed in Domoticz GUI under HW
#
"""
<plugin key="BroadlinkRM2" name="Broadlink RM2" author="zak45" version="2.0.0" wikilink="http://www.domoticz.com/wiki/plugins/BroadlinkRM2.html" externallink="https://github.com/mjg59/python-broadlink">
<params>
<param field="Address" label="IP Address" width="200px" required="true" default="127.0.0.1"/>
<param field="Mode1" label="Mac" width="100px" required="true" default="000000000000"/>
<param field="Mode2" label="Folder to store ini files" width="300px" required="true" default="C:/BroadlinkRM2"/>
<param field="Mode3" label="Get Temperature Device" width="75px">
<options>
<option label= "False" value="no"/>
<option label= "True" value="yes" default="True"/>
</options>
Thanks so much
Jeremy