I'd say that the ignition barrel at some stage suffered from the inherent failure and as such someone has merely changed the barrel to a second hand unit from the wreckers along with the key blade that operates it. They then placed the original key head onto the newly acquired secondhand key blade and instantly the issue was solved, only this left the door and boot locks inoperable with that replaced ignition blade and you were never given the original blade that suits the boot and door locks.
So as Trevor has suggested above, phone a Holden dealer that's close to you and give them the VIN number and they'll be able to look up the original key number so that you can get one cut up by any reputable key cutting service as you really don't need the services of a fully blown Locksmith that's going to ream your pockets out. This way you can obtain a key head off eBay cheaply and then have two keys that operate everything.
Alternatively you can have the ignition barrel re-coded to the original key number and get the a key cut at the same time and then just change the key head back and you'll have one key just like it was originally. I guess it all depends on the amount of cash you want to throw at it and what end result you wish to obtain.
Cheers,
VSL
PS. The Glove box key is totally different to the normal keys supplied with the car from new. That runs it's own key number altogether. Those numbers are no longer available via Holden as they lost them all in a software change some years ago and they never added all older vehicle information manually into their new database, just ECU Security numbers and Ignition Key number along with Radio PIN.