to fully know the firmware you will need to gain access to the secret menu or diagnostic screen which on earlier units needed to be enabled via VCDS/vagcom. to see if its enabled hold down setup you will see radio diagnostic pop up but keep on holding for another 15-20 seconds see if a further menu appears. If it does find the option for software and check which map and firmware you are running and post back.
As stated different versions of map have different data V6 maps have upto 4 digit first block postcode and the latest V7 maps can support full UK postcode, there are however firmware changes that will affect the nav system operation including the level of postcode detail the unit will operate.
A simple visual check if you cant get into the secret menu is to look at where the volume adjust bar is or whether or not you have a visulisation of a car when operating the fader and balance. If you check these points out and post back. you also might find the followign site usefull
www.my-gti.com will tell you about firmware versions and features they provide.
One thing to consider before you upgrade any firmware is if your unit is genuine as stolen units can be tampered with to reset the security code this can cause them to break on firmware update. There is also issues with older cars that the communication with the can gateway can be affected stopping the unit from shutting down correctly and causing battery drain issues. If your car was built by VW with the nav then neither of these problems should arise.
