Thanks for this - followed the instructions and sorted the switch with penetrating oil which seems two have disolved/dispersed the dirt which must have been in it. I'll also add that if you get carried away with cleaning it whilst it's dis-assembled like I did, then you want to ensure the motor is oriented perfectly when you put it back in, and also the cord retractor is correctly oriented (use the button position on the casing to help line it up).
Steve Burley, January 2010