Here are 2 options:
http://giftshop.scottishtartans.org/material.html
This is from Matt Newsome. He will be an excellent source of help and info above and beyond other sources.

Also:
http://www.thescottishweaver.com/
(US associate of F & K)
http://www.wooltartans.com/

The mills directly
http://www.lochcarron.com/
http://www.martonmills.com/index.htm
http://tartan-fabric.co.uk/retail.htm
(are also others)

If buying small amounts, I'd talk to Matt for wool and pester Rocky or MacHummel to see if they'll sell ya some yardage of PV.

Wait, as your in AUSTRALIA, things may be different than in US.
(any one with good ideas for Aussie tartan??)
Maybe, buying direct from mills may not be a bad idea.
Is there an Aussie distributor for any of the mills?