HI! Mark i take it that the battery is fully charged , check all wiring try working it with the rollers of the tyres see what happens . try moving the van yourself to see if the handbrake has not stuck on this might be the fault ,are the battery,s in your remote new, does the mover have a wire from the remote to the box in the van try working it with the wire .The remote might be faulty .
hope this might help get back and will try other things but not a lot left to try
cheers Duggie