I have looked further at the issue of videobridge and open fire. When you download the ofmeet plugin it downloads the videobridge and installs it in the plugins directory.
Hence when I ran a separate instance of videobridge with openfire it managed to authenticate itself with open fire and appear as a session, but in fact there was some form of conflict between the two instances of videobridge which I assume is why the ping failed. In any event I am not inclined to look at that any further.
I probably will try to run an instance of videobridge with openfire with also the rest api enabled to see if I can get them to interoperate in th same conference. I am not quite sure whether that will disable ofmeet, however. Hence I am not in a rush to look at this. My priority remains to get the videobridge REST interface to work.