[DaveNP]

If you've got a car from after about 98 or 99 the code in the key is a 'rolling code' which is reset every time the key is used so you can't get a cloned key, it's a dealer computer job at a price! If you've got a key (no help to john-sussex) you can get a mechanical copy made at the likes of Timpsons (mine had to order the blank specially) but it doesn't have a chip. It will get you into the car on its own and start the car if the original key is next to the ignition switch to send/receive the code, so one could get as many copies as you want and stick the original key inside the steering column.