Doh, and thanks.
I had bought a second hand HDR-FOX from eBay, which I had put 3.13 onto, and also took the front panel off (as it had been damaged during delivery) to glue it, taking the opportunity to remove the orange film from the display. I did put a number of packages on it, including fan. Having seen it wasn't too difficult to take the box apart to get the film off, I did the same to my existing box, and updated from 3.10 to 3.13. However, as I have now corrected, I hadn't put the fan package on to it.