hi does the van attempt to turn over m8 , i had a problem with my 03 2.5 tdi where it was turning over but would not fire, i listened to advice from different people not on the forum i might add and ended up changing the relay , glow plugs, filter and battery and guess what it wasnt any of them lol, my problem it turned out was a few teeth missing off the fuel pump belt this apparently can create a very similar fault to the glow plugs not lighting. so if i was u i would check that u have fuel going thru the fuel filter and also drain off any water from the bottom of it . u can check u got voltage going to each glow plug by using a multi meter and a friend turning the ignition over hope this helps
had same problem a week ago. messed around with all the bits, starter/solenoid, earths, checking relays, 12volts at battery, but it was knackered as not enough amps. i would say first of all get your battery checked at your local garage, then go from there.