JohnnyN You do not chip these cars. The ECU's have info downloaded to them via a laptop. Remapping as its known nowadays is carried out on a rolling road if done properly. It is also advisable not to have it done until you have finished modifying your engine so that you can get the optimum out of your mods.
JohnnyN A reputable tuning company will be able to sort you out. Courtenay Sport, Regal, Thorney Motorsport, Mid Point Garage etc. are good places to start with remapping. ;-)
Matt I had my 1.6 Astra mapped at Courtenays, very good service, took several attempts as they wanted to get all the settings correct and the car running OK.
bokel dbilas dynamics has a chip for your Astra, I think the price for eeprom is about 350 euro. If you need more info, pm me. regards, Boyan