Over the week I have installed the loom along the passenger side of the car (sills) and have decided to mount the head in the CD changer space (one of the two compartments with HDD/DVD in the other).
Have also mounted a sweet reset button to the underside of the glove box (inside it) - very discrete.
PC case itself is mounted onto my custom made shelf fitted onto the roof ceiling (along with a power distribution block).
The loom I have made will basically extend the ISO connection for the head unit to the boot.
The computer is working and formatted (no CarPC software yet). The USB hubs front and back also have their 5V power supplies and a 12V has been wired along with VGA for the screen.
I have taken a bunch of photos and will upload later.
Things still to do:
Choose a 7" touchscreen and install into bezel
Choose software and install
Complete ISO connector wiring at both ends of loom
Mount dedicated sub amp onto ceiling shelf
Install power cabling to battery