A few questions here as I have not seen any previous threads on this subject. Is it possible to play the Iphone through the Aux settings in the car like you can with an Ipod and a lead plugged into the Aux plug ? Also can you buy external speakers for the Iphone as you can with the Ipod (Bose)? Can you charge the Iphone in the car?

Yes, you can just run a cable from the headphone jack to the aux-in in your car and play it that way. If you want line-level out rather than headphones, there's ways and means to do that.

You can use any external speakers with an input jack. Just like plugging in headphones. Alternatively, you can get some speakers that have a dock that will fit the iPhone, or use the universal dock/iPhone dock for line-level out.

For charging in the car, you'll need to buy a car kit.

1. regarding AUX - if it's a 3.5mm cable then yes

2. Charging - If the charger is supported by the current model iPhone. It's very important it's not only supported by iPhone but the current 3G model as, apparently, it drops support for FireWire charging which is what a lot of third party accessories used

3. Speakers - Similarly to 2. Just make sure it is compatible.

(*edit: quite slow)

Thanks.
1) Got the 3.5 mm cable and works fine on my car.
2) IPhone is not compatible with external Bose Speakers. I understand some Iphones have blown up... Altec Lansing is the only one who supports the IPhone, I have been told.