Eureka!!!

I downloaded the latest firmware but the camera wouldn't accept it, as it already up to date.

As a completely random next step, I thought I would reset the camera, so I pressed the Initialise button.

After setting up, I've just taken a picture and the view through the EVF seems to be cured i.e. no more pixelation!  I'll keep testing and report back later if anything to add.

It has made me retrace my steps when I got the camera. It came with the v1 firmware. I set the camera up, and later on installed the V2 update.  I didn't press the Initialise button at that time though so maybe it's something to do with the update process?

Anyway, at the present time, everything is good again! Phew!!!

Thank you for your help.