In Oz we have brackets for CB antennas that bolt on the front guard and sneak out through the gap between the guard and bonnet. You may be able to get something similar.
If you decide to do that, you can then run the antenna lead out of the cabin through the LHD bonnet release cable hole. If you look in the engine bay you'll see where the bonnet release cable for LHD Touaregs comes out. Knock the bung out and run your cable through there. A bit of silicon sealant and you're away.
Cheers
Bob