This is how I fixed my dash squeak. Hope it will be of help to someone else. It is not an easy operation but a lot easier than taking the dash out. Now my dash is 99,9% squeak free. Before the noise was driving me mad. The tip about the credit card I mentioned before was actually taken from Alfas e-peer workshop manual so I did not make that one up. The problem first occured on my car after a change of wind shield, therefore I realised it had something to do with the dash rubbing against the wind shield.
1. Carefully remove the air vent that is running on top of the dash all along the wind shield by pulling it upwards. Make sure it does not break.
2. Losen the allen key found there at the same side as the noise is coming from (mine was coming from the passenger side) Pictures of the allen key and the magnesium frame that the dash is mounted on can be found in Fun starts @ 3000!
under the Tips section and Dashboard noise.
3. Put some kind of wedge (a door stopper works fine) between the dash and the wind shield near the allen key to increase the distance between them. Do not use much force as the wind shield might crack.
4. Go for a long test drive to see if the noise has gone. If it has, go to 5. If not, find another solution.
5. Now the tricky part starts. Remove the allen key (not all of them, one should be enough)
6. The next step is to place a very thick washer between the magnesium frame and the dash where the allen key used to be. I had to remove the glove compartment in order to do this still it was very tricky. On the drivers side it should be easier.
7. Remove the wedge. Put the allen key back and thighten it. Go for another test drive.
8. Hopefully the dash is now quiet and you can put everything back in place