Bob,

I can understand your plight.  Its winter here but I have had problems along those lines in the past.
I too have an '84 with no compensating relays for aircon or power steering.   They appeared later.
I overcame the problem by raising the idle with the big screw on the throttle body and adjusting the bypass screw on the AFM to compensate.  I also run the timing a little more advanced, at about 5 degrees btdc.   I have US specs so that may not apply.  I believe the Euro spec is 10 degrees btdc anyway.
Bottom line is ...raise the idle rpm a bit and make sure the mixture is spot on.    If you have power steering as well, avoid full lock.
Of course, it would be wise to check the freon pressures.  My importer mounted US unit doesnt even have a low pressure switch so you may not have these safety switches either.
What refrigerant are you using ?   I was under the impression that R12 is unavailable in Oz.

cheers, Steve Cotsford