A few of us have discussed this on a mk6 forum. I have a Pure Highway on my other car, it uses a screen mount ariel and the cable can be hidden behind the A pillar trim. I have my Highway hidden away in the drivers knee bin above your right knee and the power cable is just run behind the trim and carpet to the ciggy lighter. It's okay but not perfect.
The only real option I've seen in the UK to get around this properly with the RNS costs £395 fitted and will work with the steering wheel buttons and MFD screen in the mk6 but I don't think it works this way with a mk5. This is through SatNavSystems, they may have a set up that works with the mk5.
