how can i fix my 03 almeratino 1.8se?

my car wouldent start then i realised that the imobilser light on dash board was flashing after turning on and off sevral times it stopped and would let me try an turn car over but wouldent fire up then the imobilser light would start flashing again. got recovred by the rac tried second key an same again would turn over a few times but wouldnt start. rac man seems to think its the imobliser module. hope someone can help me out. thanks.