My problem was different to the others so thought I'd post. My creak came from the screws holding the front display panel on to the front of the radio CD. A good way of checking it's this as oppsed to struts etc is to press the plastic panels while driving along, this should stop the rattle.
If this is your problem remove the air vents as described elsewhere but not for me the metal clips holding the air vents in weren't visible so gently push a screwdriver through the holes in the top of the inside of the cowling through the second louvre down so you can get the angle and you'll be OK.
Once the heater vent assembly is out, undo the Philips screws holding the radio CD in, unplug the connector and ariel assembly and you have the unit out.
If you can move the front plate up and down from the unit it will creak and the screws need tightening. Do that and no squeaks, job done.
Jason