Well, I got my empeg back this morning, just over a week after I sent it to the hospital (aka Cygnet Court, Cambridge). Yay!- the display works again.

Hugo did his trick with the glue on the shaft to make the knob grip it. Absolutely no problems now, and it comes off easily if necessary. He sent me a pic which shows what he means which I've attached.

Once again, kudos to empeg's level of customer support.