To all those of you who have this problem with particles on the sensor: Follow the disassembly guide already provided on this site till you remove the dark plastic (not metal) cover that is underneath the LCD screen. Now remove these three very obvious philips 00 screws that hold the sensor unit - you don't have to unplug it. Once the screws are removed you can lift off the sensor unit and have a close look at the sensor surface (you may be in for a surprise, how much dust has accumulated on that supposedly sealed area). I took a fine sable hair artists brush to wipe all the dust off - purists might cringe but it worked fine for me.
It has been mentioned for other camera types that the exact placement of the sensor unit is essential for the picture processing, i.e. the tightening of the sensor screws can influence the picture quality. I am not sure if this is true for the WX80, still having had that in mind I made a mental note, how tight the screws were in their seatings.
When reassembling the camera bear in mind that the reinsertion of these two LCD screen cables is a bit finicky, or at least it was to me.
A remarkable improvement of your picture quality should be the result, one is still left wondering, why Sony didn't take better precautions to avoid this problem.