Silly question but i have just found a water leak from the hose going from the front of the cylynder head to the heater but cant see how to undo it at the heater end where it comes out of the bulkhead ????
My van is a 1994 2.5di, and has jubilee clips, you might need to pull the sound proofing an inch or so away from the pipe in order to see it.
Good luck Mike