Check the TEMP directory (you can get to it quickly with %TEMP%). Arduino 0015 puts intermediate files (except library ones) and target files there.
Hey, that was it - thank you very much.
So, it's a bit of a kluge at the moment but I can write code in the arduino IDE and run it on the ATtiny84. I'm guessing it's still to do with avrdude and my cobbled up programmer.
Works though, and I'm hopeful it won't be too hard to tidy up what with my mad avrdude skillz and all. Thanks to bohne for the ide integration and to drug123 for the four-jumper programmer idea.