Try shifiting your question into the CARS section you'll likely get a solution. You're in the Motor home and Caravan section those without these won't be reading this section will they!
However it could be a solinoid fault. And you should be able to lock it manually by removing the fuse from the main board that operates the central locking leave the drivers door unlocked when you remove the fuse and try locking and unlocking the passenger door and tailgate. If they work then you can lock the drivers door car safe and alarmed, or should be. This will make the car safe while finding a solution from the right forum section.
Nobby, March 2008