Thanks for your comments all. This seems to have become needlessly complicated: I thought I was posting a simple piece of advice.
To sum up:
All the dials stopped working at once.
The fuses were OK.
The speedo started working (I hadn't mentioned this before).
I removed the instrument pod and cleaned the connector contacts.
I took the unit to be fixed. They told me that the 'motors' had seized, and that this is a common problem. It now works fine.
I conclude that it was a problem internal to the instrument pod, maybe 'motors', maybe something else. It is now fixed.
Before taking it to be fixed, I decided that, despite a lifetime career in electronics, I was not willing to take the risk of b#ggering it up at a cost of >£600, but to pay £125 to get it fixed.
End of story.