Thank you both.
I did try "pressing the button on the drivers side pillar next to the seat before locking it manually, then unlock" and the alarm then still sounds imidiatly on turning the key.
I'm happy for the alarm to set, the real issue is that you can't unlock the van manually without it going off.
I've seen some other posts saying it shouldn't go off when unlocking with a manual key or opening the door as long as you put the key in the ignition shortly afterwards. This would be a acceptible solution, but this isn't what it saya in the handbook or what happens.
It makes me wonder where there is a key hole on the drivers door if using it with any key instantly trigers the alarm?