Argh! Dust on sensor.
 

Don't know how this happened, but somehow managed to get some big globs of dust on the sensor. I know it is the sensor, because the globs are perfectly in focus and bounce up and down as the image stabilizer does it's thing.

Any obvious/easy way to clean it, or does it need to go back to Sony?

That happened to me on a motorcycle trip I just used a can of dust off worked fine after that.

How did you get access to the sensor? Did you take anything apart, or poked the nozzle in through the tape hatch?

I just opened it up an stuck the nozzle in and dusted everything I could reach. I was on a motorcycle trip across the US and knew I would never get another chance to shoot a trip like it again. So I took the chance and it payed off. Make sure you blow out the eyepiece also. Good luck.