I have found that most of the later VAG audio units will recognise themselves as belonging to the car after a short time of the key on. Most say SAFE and then switch on while on a test drive. This only applies if it is the original unit for that vehicle. I have only needed the code if it's a used headunit that has been fitted. In fact most makes that have the VIN stored in the headunit recognise they belong to that matching vehicle when they are active on their network. I don't know of any one providing VAG radio codes for free and a lot of the internet based paid ones are a waste of time. The guy I use for decoding VAG units usually has to read it from the chip. Not sure if any of the key pin extraction kits can pull a radio code though so maybe someone else can advise on that.

Liam