DeDietrich Cooker hood extractor switches?

Brilliant extractor but the light and fan buttons have become very temperamental I have tried to remove the panel they are mounted on without any success. I feel that the push button switch contacts need cleaning and then it may work. Have use aerosol contact cleaner and small brush but not a lot better. HOW DO I TAKE THE UNIT TO PIECES AND CAN IT BE FIXED OR REPLACE. I would be willing to purchase a new switch panel if available. dhg356xp12 is the number. Any help appreciated