i tried disconnecting the battery again, left it for half an hour, then tried the re-sync:
van was unlocked, pressed and held interior door lock but immobiliser light did not turn to constant, held button for about 1minute to check it wasnt delayed.
so, theres something up there, switch works fine, just didnt change the light from flashing
also, the black fuse in the engine bay for the engine management, when ignition turned on/off this makes a click noise and you can feel it switching, so am i correct to assume this is working fine, or could it be faulty anyway?
stealer wants £15+vat for one!