CASA approval granted!
I got a phone call from CASA this morning to let me know that approval for launch was going through, and to ask a few questions about the tracking of the balloon. Hopefully I'll receive written confirmation today, and we can then start to look at organizing launch. 
Likely we'll aim for a weekend launch to make sure everybody is available - unfortunately current predictions do not look good for this weekend, though we may be able to launch in early February - but this is too far away to be able to predict at the moment.
CASA approval ongoing
Unfortunately I heard back from CASA today that approval has not yet been finalized. This means we can't legally launch this weekend. At the earliest we may be able to launch Monday/Tuesday next week, as CASA will only process my application during business hours.
Who knew a simple approval would take over 2 months to process? 
Launch delayed
Picked up an E size cylinder of Helium today - many thanks to Gary from the Elizabeth branch of Air Liquide Australia for making it all happen. I've also made up a balloon filler with a regulator for the cylinder & some hosepipe + PVC tubing, which looks like it will do the job well.
I have been hoping to launch this Sunday, as the weather has been looking very favorable. However, I heard back from CASA today, who are not yet done with processing my application. Hopefully this will be done sometime next week, and we can then start to look at launching. 
Quick update
Did not yet get around to doing a tethered test due to the weather here - it's been in excess of 40 degrees C for the last few days.
Visited Adrian and did some testing of the telemetry & found a few bugs - the most notable being that the temperature sensors were failing once the GPS achieved lock. Reason for this was that the interrupt driven software UART to the GPS was throwing off the delays enforced to give the temperature sensors time to take their readings when data was being received. I've since fixed this, and moved to a more accurate timing method for the RTTY telemetry.
The pressure and humdity sensors have arrived and have been connected. The pressure sensor seems to be working correctly, I need to test the humidity sensor against an environment of known humidity to make sure it's also working.
I've started work on a GUI frontend to track all the balloons sensors. I'll upload screenshots of this soon.
Currently awaiting final CASA approval, launch in the next 2 weeks is looking promising, with good wind conditions. Will finish off the tracking page soon & have a few ground based runs to ensure everything is in working order.
Predicted flight path
Current state of affairs
Haven't had much chance to work on the project or update the blog in the last couple of weeks due to the festive season being in full swing - aiming for a launch in a week or two though, I'll set a tentative date soon.
I was given a Sparkfun voucher for Christmas(thanks Holly! ), which will go down a treat. Sparkfun are selling a humidity sensor which I'm ordering for the payload - this simple analogue sensor looks really easy to use, having an almost linear output.
Sparkfuns humidity sensor breakout board
I'm also ordering an MPX4115 pressure sensor from Farnell - a (cheap) absolute pressure sensor with a range from 15kPa to 115kPa. A minimum of 15kPa means that I will only have accurate pressure data upto 45,000 feet, but I don't know of any other sensors which are capable measuring lower pressures in the same price range.
MPX4115 pressure sensor
I purchased a piezoelectric buzzer to be used as a warning tone when the payload descends below 1 or 2km, and to help us find the payload in case it lands in trees or scrub. This little buzzer can run on anywhere from 1-13v, and draws less than 10mA at 5v. Even on a single AA battery, it's very loud!
Piezoelectric buzzer
My balloons have arrived from Kaymont also. I'm planning on doing a tethered test of telemetry & software this weekend, I'll send an email to everybody who's contacted me regarding tracking. Tethered balloons are bound by maximum altitude restrictions, so range will be limited, but hopefully we should be able to get an idea of how well everything is working.
Kaymont balloons