So, more key learnings (they keep coming which isn't a bad thing I guess):
Headsets - Absolutely critical to have audio equipment tested and working on the PC you will be using prior to the meeting. Don't change PCs once you know it works. If all those tips on checking mics have been done and you still can't hear or be heard, well what can I say, other than buy a new headset.
Dial-up presents problems - much better using broadband if you can.
Bandwidth presents problems - this will cause the intermittent drop out of audio and presentations. Have to be patient on this one - we can't change this.
Echos - best to not lock audio on unless you are actually talking. With everyone locking in audio you can pick up sounds in each other's background, even breathing. Also draws on more bandwidth.
Sharing files - powerpoint presentations need to be fairly simplistic and certainly not too big otherwise they create a life of their own (gosh, is that an understatement!).
Perseverance will win the day, and our experience is certainly allowing us to experience what might happen with students at the frontline so that in itself makes it worthwhile. What always bothers me though is losing confidence in e-learning per se because of some initial technology woes. We can do it team - hang in there!