Immobiliser

My name is Keira, I have a 1994, BMW 316i, 1600 engine with 133000 n the clock. I am having a bit of trouble with my immobilser, and therefore cannot start the car! And can only open the car with the key manually, my first thought, was the batterys in the keys, which I have replaced, and still doesnt work. I have tried openening and locking the driver door with the key, I have also tried leaving the key in the ignition for ten minutes. Neither have worked, however, the immobiliser light inside the car no longer works, and when the key is in the ignition, I have noticed a tapping sound Ive not noticed before. I took a brief look at the fuses, but all seemed fine. Can anybody please help as I am at a loss? ?