It seems like most here are in agreement that I should be looking for the latest highest spec I can so that's where I'm going to focus my search.

You can download the advertising PDFs on each on the year model marketing dribble. I have most of the PDFs

MY13 onwards is a different beast, at the age these cars are now. This is the oldest car I would buy.

Fortunately down under we have the Si4 petrol engine as an option to the "fish & chip" oil burner! Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

The 2013 on models are superior, and all SD4 are auto so that should make your search easier. The uprated spec is nice but the drive is so much smoother and quicker, when moving off it reaches 30 so quickly you can easily be over the limit in a couple of seconds or so.
Quite how they make it pull away so fast is unbelievable, and even when towing my ton and a half of caravan it keeps up with the traffic flow as if it were solo.
Get one, it may be a bit long in the tooth now but I can tell you, it is a very nice place to be and always brings a smile to my face   MY2014 SD4 XS
Ipanema Sand

MY10 TD4-e GS Manual
Lago Grey Now retired after 8 trouble free years

Don't forget that the 2011 model bought in the DPF and with it the 2011 hesitation problem so best avoided. I agree about the post 2013 models though, definitely best of the bunch. In fact if they had kept making them I would probably be looking for a new one now rather than a suitable petrol DS which is my current project. ! 3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE