My 2004 2.0d x type all of a sudden wont start, just a clicking noise and all my dashboard electrics started going crazy and battery light came on. I got a jump start and the car started first time, but still battery light stayed on...then went out, all dashboard electrics were fine for about 6 miles then went nuts again and my battery light came back on and stayed on. All the belts are present, and the car start first time all the time from a jump start, but when trying to start it on it own with just its own battery there is nothin but a click.

 

That is pretty much what ours did when it ate a cell in the battery. A voltmeter is your friend at this point. Check the battery voltage, charge the battery fully and check the voltage a few hours later, start the car and check the voltage with the car runnng. Roughly a good battery should be 12.6 or very close to that and the car at idle when running should be 13.2 or above. You should be able to take it to most any auto parts store and get them to test the battery and alt in the car if you can get it there

 

A fully charged battery should show 12.6v to 12.7v a couple of hours after charging.
When starting the engine the voltage should not go below 10V. If it does then a new battery would be the way to go. When the engine starts it should show upto 15.3v and then drop to 13.6v after a few minutes. This would eliminate the alternator. These cars have a smartcharge system so only charge the battery when called for when driving.

Roger