Afternoon jospanner sounds like good and bad luck at the same time with the van, but more to the point the fault seems more like the common problem of the rear wiper wash hose leaking/breaking and sending water over the boot handle mechanism.
In there is a micro switch for the clusters to read if the tailgate is open or not, i had this problem intermittantly and left untreated will lead to the mechanism seizing up not locking/unlocking and no longer being able to open the tail gate. take the trim of and have a good look for any dampness and leaks.
on a second thought thou it may be a split wire in the tailgate rubber boot wich carries the wires both worth a look imo good luck [Y]
In there is a micro switch for the clusters to read if the tailgate is open or not, i had this problem intermittantly and left untreated will lead to the mechanism seizing up not locking/unlocking and no longer being able to open the tail gate. take the trim of and have a good look for any dampness and leaks.
on a second thought thou it may be a split wire in the tailgate rubber boot wich carries the wires both worth a look imo good luck [Y]