You have to remove the padded shelf from on top of the dash, and slide your hand down behind the dash. Just below the bottom of the screen, you will feel the nut holding the washer jet on. If your hands are small enough, you can use a spanner to undo it. I had to clamp a pair of large molegrips onto the outside of the washer jet to stop it rotating with the nut. If you can't get your hands onto the nut, you will probably have to move the whole dash away from the bulkhead.Who knows the best hard way then?
Very easy and that is what I have done. Although need to do it again as drivers side has stopped working now!