Back in July, there was some discussion about key cutting and I asked a question regarding a replacement key for my son’s Corsa after the blade on the original had broken. http://www.honestjohn.co.uk/forum/post/index.htm?t=85898

I was interested to know if a new key (obtained from e-bay) were cut to match the original, would the old transponder work if the broken key remained attached to the key ring. Well, we’ve just got round to sorting it out.

As no one appeared to know the answer, we forged ahead and bought the blank key (containing a blank transponder) from e-bay for £7.99 and the local shoe-repairer/key cutter cut it to match the original spare for £4.

We tried starting the car with the new key, keeping the broken key body on the same key ring – but it wouldn’t start. We then tried splitting the keys, and putting the old transponder into the body of the new key. I was thrown at first because I expected the transponder to be more obvious – in fact; it was a small insignificant black object, similar in dimensions to a centimetre of matchstick. It was housed in a small recess to one side of the key.

After this procedure, I was delighted when the car started! It would appear that the transponder has to be held in exactly the right position. Keys and associated issues seem to be a money-spinner for the dealers and I shudder to think what we’d have been charged if we’d sought their help.

As we have two Vauxhalls in the family. I obtained the hardware and software from the source you posted to enable me to clear old keys from the system then program two more each for two cars. Didn't cost much and it does all the diags too.