UK spec cars only come with efficient driveline at the moment, which is a fancy name for the system that is currently used in the Fl2, only the DS uses the latest haldex which is 4KG lighter than the Fl2 unit.
The car at standstill, the centre coupling is locked then opens as it pulls away. All the off road trickery is controlled via the electronic centre coupling, if one wheel is spinning the traction control system applys the brakes to that wheel and directs drive to the wheel with grip, in order for it to work though you need to give the car some revs and allow the wheel to spin to tell the car what it needs to do. With efficient driveline there is always a percentage of drive to the rear.
Active driveline purely adapts between 2WD and 4WD, again it's 4WD from a standstill but speeds over 22MPH a clutch disconnects all the 4WD hardware and the car drives as a 2WD with 4WD engaging when required within 350 milliseconds. There are two clutches, one either side of the rear differential which can direct torque to the wheel with the most grip, also the rear axle can be locked for maximum traction.
It's not the most advanced explanation and I'm no expert but it's the basics.