Go down with screwdriver about 18mm then turn screwdriver 90 degrees ... this should have the effect of "pushing back in" the notch bit on the yellow plasdtic button ... this would then seemingly "jam in position" the yellow button, but now "coerce" the yellow button upwards until it is out (perhaps with one or two more small flat screwdrivers popping in about 2 mm to wresstle switch out) ... from here you will see a screw - mine was a star shaped head but i used a small flat screwdriver on this which worked fine. Then lift out by pushing up on power cord ... hope this helps ...
Steve
November 2007