Doug, welcome to the Forum as a new iMiEV owner! I have fond memories of finally seeing Cape Byron lighthouse as I sailed up the coast, and Byron Bay is probably the most laid-back community in Australia ...
I take it you're further inland?
Wow, you covered a number of topics in quick succession:
You are SO lucky to have 240v in Australia, and I strongly suspect that you will find it adequate for almost all your needs ...
You will soon be able to judge your distances and charging times, and simply remember that slowing WAY down (<70km/h) has a fantastic effect on extending your range. After you get over your initial hot-rodding exhuberance, you'll find that a featherfoot does wonders for range. Just try not to go below two bars on your fuel gauge to always leave yourself a cushion... 90km is a good stretch, so really take it easy the first time you try it, and opportunity-charge if possible... just carry a long extension cord and your Mitsu EVSE, develop a good eye for spotting outlets, and then learn to sweet-talk the owners into letting you use one (and always offer to pay...). Most people are so fascinated with an electric car that you should have no problem, especially in friendly Australia.
You will have no problem meeting your Off-Peak charging timeframe, as I think you'll find that five hours at 240vac will be more than adequate for your overnight needs.
Vehicle-to-Grid is another topic you touched upon. Technically, not a problem and you could undoubtedly rig up a system that would work. All it takes is time and $$$ ... perhaps a solar photovoltaic setup would be easier and cheaper? BTW, I attended a presentation recently on V2G which presents a good case for stabilizing the grid if thousands of EVs are utilized: http://www.eaasv.org/files/TGage-EVgrid_130615.pdf
Back to the original topic, I guess you have CHAdeMO in you iMiEV and if you're ambitious you could indeed try the do-it-yourself CHAdeMO route - there are a number of separate online groups with working hardware, for example -http://www.diyelectriccar.com/forums/showthread.php?t=59210http://code.google.com/p/open-chademo
That it seriously time-consuming stuff to play with.
Finally, back to your original question, don't know where to get a CHAdeMO connector.
All the best, and enjoy your wonderful new car!