Ive been suffering from the same problem as a lot of people here.
No or very little water coming from my water jets on my '03' 2.2 DTI SRI.. So for the last 3 days ive been trying to figure out what was wrong.

For those still not getting it going here could be the solution, well it just worked for me.

After removing T20 screws from wheel arch and releasing part of the bumper to show water reservoir you should:

Step 1. Remove pipes from side of pump

Step 2. in the corner piece (connected to the pipe) there seems to be a crap one-way valve to stop water returning to the reservoir. this needs to GO!!! a small flat head screw driver did it for me and i not have jets that can shoot 5 meters over the car!

Step 3. Pop the pipes back onto the pump and test

Hope this helps and GOOD LUCK


P.S. Message me f you need pictures of where i mean (there not very good tho .. )