No Security Codes/Radio Code exist for the Astra K
Lock-N your Sales Man is telling you porky pies.
I work in the Service Department of a main dealer. Please see my article on Key Codes here:
http://www.astrakforums.co.uk/viewtopic.php?f=11&t=146
Astra K's are not supplied with Radio Codes at all.
There is no security pass for any Vauxhall car from Astra K onwards. All key programming/software updates are now done by the main dealership logging onto General Motors database via software called TIS2WEB using the MDI/Tech 2 diagnostic tools.
This is a new move by GM to prevent independent garages from being able to program keys/carry out illegal software updates. However for customer convenience purposes it means you won't lose/forget the Security Code/Radio Code.
Each radio unit/car is still programmed with a unique code however it is verified as genuine by General Motors central server. This takes the hassle away from the customer but reduces the ability to get 2nd hand or re-programmed units from eBay, etc.
The Astra K is quite an advanced car and as things improve in technological terms GM (and most car manufacturers) want to reduce the chance of hacks/dodgy software being introduced into a vehicles systems.