Key Fob Problem?

ok, read all through the problems and mine isnt there. I have a 2003 astra 1.7cdti, my old key fob never worked so got another one from ebay listed as working fine. press the buttons and the red light iluminates. i can lock the car with the key, i can unlock the car with the key, everything and i mean everything works as it should on the car, fuses arnt blown. My problem is this, the fob still doesnt work even after reprogramming. Any ideas? also, where, if it has one, is the receiver for the fob ?