Olympus SZ-16 sensor cleaning.
When I got home I carefully cleaned the lens, not easy with old eyes so I used a loupe to see, but the spot was still there afterwards, so with an unusual spurt of energy I decided to see if I could clean the sensor.
This is a reason for buying a camera with a removable lens, perhaps even the best reason but the convenience of a fixed lens camera is wonderful. I've had this happen before with a Panasonic so it's not brand specific.
Circled in white is a much larger clip that must loosen to remove the screen, it's much easier to manage than the little one.
Circled in red are the screws that when removed allow access to the sensor. The whole black assembly has to be carefully juggled so it hinges out a bit along the line of the three ribbon cables shown to it's right here.
Hope this helps someone but only try it if you're prepared to write the camera off if the worst happens.