Many GT and 147 owner complain of a squeak/cracking noise that seems to come from the A pillar area on the off (drivers side) of the car. In some cases the issue gets worse when the heater is on the windscreen or in cold weather.
I have resolved this issue as follows:
1. Carefully remove the air vent that runs the whole length of the dash (put your fingers in the vent and gently pull it out)
2. Unscrew the (allen head) bolts carefully ensuring they don't fall in to the vent system. You will see the bolt has a rubber and metal washer.
3. Remove the rubber washer and replace this with another metal washer of the same size as the existing metal washer. Replace and tighten the bolt with the two metal washes.
4. Replace vent and enjoy a crack/squeak free ride.
My '04 plate GT is excellent. I got rid of the rear hatch noise easily after an infuriating month of trial and error.
Only issue I had was recent EGR issue (no smoke but nearly killed me on a roundabout no power for 10secs). EGR valve, cam belt + waterpump were changed yestersday at Mangos - drives like new.
Great car with "drop your draws" looks.