Just for those who are interested, I have finally got around to uploading my version of the 'tiny' core for Arduino. Along with that I have included my version of Optiboot which works with the ATtiny84 and ATtiny85 processors (The optiboot version includes TinyTuner built in to calibrate the oscillator allowing a Software UART to be reliable).
The Core is hosted on github @:https://github.com/TCWORLD/ATTinyCore
Beta testers are very welcome as there are probably a few bugs in it which need ironing out (with the exception of the bootloader which is fully tested and functional).
I have also uploaded the fix for the PCREL error to the repository so it is easy to find.