Ford Focus Central Locking Help

[Garybaxter1982]

Hi please could any one help me, I've just bought a y reg 2001 ford focus 1.4 five door harchback, now this model does not have a fob on the key to lock and/or unlock it us just a torch key I have. The problem is when I go to unlock the car from the drivers door it only unlocks that door and I have to enter the car and manually unlock all the other doors, now this happens most days although I was sitting in the car cleaning it and all of a sudden I heard the car unlock all the other doors by itself?? Like i said It locks sometimes and other times it just doesn't, what can I go yo resolve this problem as its not very reliable ??