BlueMotion2 Owner. Questions

[Bikerz]

Hi all

Just got a Candy White 9N3 Blue Motion 2. 2008 plate 1,4TDI 80ps

Seats - I have measured mounting points and seems my mk3 sirocco ones will bolt in so that means all mk5 or mk6 seats will fit, true?
Stereo - How do I remove head unit (cant see key holes to remove)? What is speaker setup? Is there mounting for 6.5" up front and in back and tweeters front and rear?
GTI Headlights - Why do people change for them? I can only see they have black backs rather then chrome, is that the only reason? They arnt projectors?
Rear Beam - Anyone taken one from a GTI or such to get disks on rear? (Yes I know rear only does 20% of braking (about)).
Brakes - Front brakes that fit under 15" wheels, can I upgrade to something larger? I know the 312's wont clear 15's.
Wheels - I want 15's! What size wheels / tyres can you fit front and rear roughly? I know it depends on how low you go!

Cheers All - Sorry I know its a long list, been on here a while and not seen much about this stuff.

Sheldon