Transit 54' Plate, "85 T260" Lock Problems?

Any idea's Anyone.?
My Ford Transit 54 Plate (85 T260) SWB, has a lock problem. I have no central locking fob only a standard key. I'm unable to unlock rear doors with the key but can from the inside, the side door unlocks after some twiddling of the key, this also locks when you close it, the driver and passenger doors lock but won't unlock with the key.

Also cigarette light does not work.

Any advice would be appreciated.