Just had the same problem. After reading your question also I had to go and investigate. Opened boot window. From the inside ease the plastic trim away. Its held in by about 5 plastic clips. Gently lift and slide hand or flat bladed screw driver in to ease the trim away. Once it's off there are four bolts requiring a 10mm socket. undo these close the window carefully and lift the spoiler away. You can see the hose and jet. Just push the hose back on. It may be worth just checking your jet is clear before re-assembly.
320dj, August 2008
The washer jet has a non return valve in it and it gets blocked,
Blow it through with an air line and refit.
Ps make sure you blow it through in the same direction as the water would flow
