In message , jkn
writes

FWIW I have a small collection of 'wires' cut from old guitar strings when
trying to clear blockages like this. You then have a variety of diameters, and
the wound surface on the larger diameter strings is good to abrade the inside
surface.

Brilliant. Thank you, I'll try that. Son is a guitar fanatic, so will
doubtless have old strings lying around.

For the avoidance of doubt, yes, there is a good flow of water, just not
through the final jet. The rear wiper had broken, so I removed and
repaired, and tested without replacing the cap over the spindle. Flicked
the switch and was amazed to see a jet of water shoot out. Not being a
top of the range model, I had always assumed a washer was not fitted at
the rear. Now I know it is there, I'll try the guitar spring trick.

The drill I tried was very tiny - probably less diameter than the
average sewing needle.
--
Graeme