L Reg Astra

Not from that description!

Removing an immobiliser is pretty straightforward (assuming it is not a factory fit). Follow the wires from the thing on the dash board, till you find the immobiliser ecu. Then trace the wires from that, you should have a live, an ign live, and an earth, leave these alone for now. The other wires should come out in pairs, these will go into the loom somewhere, and will join to a wire which has been cut (e.g. when the immobiliser was installed, the feed to the starter motor will have been cut, and the pair of wires from the immobiliser used to join the break). When you have found where the immobiliser is joined to the loom, re-join the cut wire, and remove the pair of wires to the immobiliser. When you have removed all the pairs of wires (there can be up to 3 pairs, fuel, ignition and starter), and the car starts and runs without putting the chip in, you can then cut the feeds to the immobiliser, and remove the ecu and thingy on the dashboard, this last step is not essential, you can leave the thing in place, complete with flashing light or whatever, so it still appears that you have an immobiliser.