Yes the Leaf does support full postcodes. I didn't know the Ampera didn't... that is a shame. As you say, perhaps a software upgrade might fix that.
Nissan have been OK regarding fixing issues but not so pro-active regarding changing functionality. Problems have been fixed quickly but the software is still pretty much as it was at launch a year ago on the Leaf. I hope GM are more pro-active regarding the Ampera.
One cause for optimism is that having driven the pre-production Ampera at the London docklands event and then again at the ePioneer event a few months ago there are several changes to the software that I think I have spotted. I am not 100% sure about it but I believe that there have been several changes to the way range info is displayed. If they are making those kinds of changes so close to launch then there is hope they will make step-changes after launch with the software.
Fingers crossed
