OK folks,
It's been a couple of days now and i think it's all good so i can finally conclude this rattle hunt.
Note that this worked for me but may not work for you. Take the time to read the areas i have examined and check all possible sources one by one.
It was the damn HVAC aspirator junction. The rubber hose with the U bend weighs more than the aspirator itself. It also extends a good 5-7cm from the aspirator. Additional weight, plus the distance from the pivot (aspirator junction) magnifies the slightest wobble or vibration into a significant one.
Solution? Tape the hose down to the body of the HVAC unit. You can use some good electrical tape (i used some 3M stuff i had in the car) or duct tape. I will source some high-temp tape to make it a more permanent solution as it's near the heater pipes and also subject to temperature fluctuations (eg. if you turn the heater on). The adhesive of electrical/duct tape may not hold securely in the long run when subjected to temperature cycling.
Pics:
ImageShack Album - 3 images
NB, I am from Australia so this was on the driver's side (right hand side). I believe on the LHD models, the aspirator will be on your driver's side. Locate the small grille near your right knee and look under, follow hose.
Let me know how you guys go with this
I'd like to hear.