i've got a tomtom with the RDS remote and the hands free mic
i have mine to the right hand side of the cockpit, the wire for the mic, is tucked inside the linning of the A pillar and the mic is clipped to the drivers side grab handle.
the RDS wire runs across the bottom of the windscreen with the slack, tucked down the dash.
I only use mine on battery, as the journeys i do are shorter than the battery life, and if i'm going further i can just use the power cable, if you want to hard wire it, i'd suggest that you run the wire through the fuse box eg between the fuse box cover and the door
this link might be of help
http://forums.vwvortex.com/zerothread?id=2672579