Quote:

Land Rover developed a body construction method, marketed as Integrated Body Frame (IBF), where the engine bay and passenger compartment is built as a monocoque, then mated to a basic ladder-frame chassis for the gearbox and suspension. Land Rover claims IBF combines the virtues of monocoque and ladder-frame .

DG wrote:

Fundamentally the same as the D3 ....monocoque mounted on a ladder frame

To elaborate on the slight difference, the chassis on earlier D3's (think pre 07) is slightly different to later D3's and the D4.
There's an extra (beefed up ....... or should that be horsed up) extrusion into the front wheel arch.
This is to prevent the wheels from entering the front survival cell in the case of severe frontal impact.
The fitting of larger spec wheels/tyres, types/sizes can cause problems where the tyre will foul this extrusion, but be perfectly ok on earlier models.

disco_steve wrote:

Should I only sit in the rear of my 06MY D3 from now on then

Just enjoy the better clearance for your front wheels and don't think about the rest
Not very gentle for the other road users but in case of a severe head-on collision, the expectable weight difference should be a better protection than the additional metal.