Heavy clutch on diesel Renault Grand Scenic?

We have a 2006 Renault Grand Scenic 1.9 Diesel which has covered 39000 miles which has a very heavy hydralic clutch. The problem we are having is that the clutch is so heavy that on occasions we are struggling to change gear. Our Renault dealership have measured the clearances and have told us that there is nothing wrong with the clutch. The problem has existed since we owned the car at 12000 miles. Someone has suggested that the pressure plate is faulty. Any ideas?