Diesel engine wont start on the fiorino

Right first of all i have to tell you a little story...

Two weeks ago i stopped at the petrol station to get some diesel in the van, i stopped on the wrong side of the pump though so i tried to start the van, but it wouldnt start . I pushed the van to the side of the garage and had to call the AA out, and they said that i needed a new battery and the alternator is a bit suspect. So last week i got a battery for the van, and used it 5 times before trouble started again, i tried to start the engine but it wouldnt go, so i checked the starter motor and the push on connector was loose, i pushed the connector back on but didnt try to start the engine (battery was flat from trying to start it). I put the battery on charge last night, and this morning i fitted the battery to the van, but as i turn the key (after the diesel light goes off) the starter motor is turning, and its trying to start, but it cant quite make it. Can anybody please help me sort this out

alternator
glow plugs

longshot but could it be the diesel pump full of water or blocked? happened to my dads old clio

Well i got the engine to run but only after it stopped the first couple of times (ran for a couple of seconds then stopped). The third time i started it it tried to stop but i put my foot on the gas pedal to keep it going and it recovered nicely , i just hope it runs ok tomorrow as i am picking up some ladders from machine mart.

Calling all disel owners, can you please help me. The first time i turn the key the van starts for a second then stops, then i try about 4 times more but each time it just turns over (doesnt try to start these times), but if i am lucky and it DOES start, the revs dont go up even though the gas pedal is pressed to the floor. I have to lift off the gas (the engine sounds like its going to stop) and then press the gas pedal again, it takes a few seconds but eventually revs properly. I am totally and feel like my head off a wall