After disconnecting the batteries while I worked on my car, I found that the passenger door would not open from the outside, once the batteries had been reconnected.
I have done the Wokke door lock modifications and therefore was certain there wasn't a mechanical failure. I remembered seeing somewhere that the central locking can sometimes go out of synchronisation.
To re-sync the central locking I inserted the key into the drivers door lock, then turned it fully anti-clockwise and held it in that position for a few seconds. The door windows closed fully and pushed up against the top door seal and the locks clicked. I then unlocked the car with the remote button on the key. The passenger door opened perfectly from the outside - job done.!