Vous devez m'excusez, mais mon francais n'est pas si bon pour m'explicer quand je parle des voitures. Donc, si il ne derange pas, je vas m'explicer en anglais...
This is how I have done the GPS-part of my clio.
Everything is connected to the switched 12v of the sigarette lighter, so it's only powered when the ignition is turned on. The bluetooth GPS-module has an auto-on function, so it switches on when it detects power.
There's also going an external antenna to the rear, under the little rear spoiler. The cable is long enough to route it trough the rubber gommet between the trunk and spoiler, all the way under the headliner to the front cabinet. Since the antenna is magnetic, it doesn't shift around under the little spoiler. (will take a picture of that soon)
This way I have excellent and fast reception of the GPS signal. I have an athermic windscreen, so if it just sits behind it it sometimes takes long to get a fix.
Here you see how it is all fixed in the cabinet. You also see a second connection, that is for the power to the PDA.
The PDA now has a proper 12v connection and not those idiotic sigaretlighter plugs! Used a jack plug for it, tnx to a buddy for soldering. And modified a cheap pda-connector of of ebay for it. And some headshrink & snakeskin to finalize everything.
The holder for the PDA is one from Brodit, made for the clio.
Cyril_fr, the antenna costed me €20, and about an hour of work to get it all in.