S4 B7 options and service advice needed

[Rustydonkey]

Hi all,

I am soon looking to buy a B7 S4 avant. I have a few question about servicing and options.

What is the difference between satellite navigation and satellite navigation plus?

What is the difference between Xenon, Xenon plus and adaptive lights?

Do they need a cam belt changing or is it chain and when should that be changed?

Who are the best independents around the Midlands for servicing?

Thanks for any replies in advance.