You could also take a look in the For Sale Section of Martins Defender2 forums - mostly Pumas (the one with the bump on the bonnet and the stonking 2.4ltr Ford Transit engine). Something really important to check when /if you go for a test drive of a pre-owned car is that the Diff-Lock works properly. A car that has been regularly offloaded will probably be fine for this but one that is used for the school run or doggie walking may have a seized transfer box - all you need to to is drive the car, using the short stubby gear lever move the lever across the gate to the left while in neutral and select either difflocked High or Low box and then check that the orange icon on the dash comes on, drive a very short distance (otherwise you might wind up the transmission and damage it if you are on the road ) then shift back to the Normal box. If the Difflock light doesn't come on then there could be expensive gearbox repairs to free it up. When returning to High box sometimes it can take a while for the diff lock light to go out, just drive it gently until the light is extinguished, if it doesn't then the Diff lock will still be engaged and you could damage the transmission.
Here is what I had done:
1) Two benches - 2 people each side - I had 3 adults in the back offloading on Sunday, it is't comfortable and if you are going to drive any distance with people in the back either the proper County Bucket seats or the folding forward facing seats would be way more comfortable
2)The "new" side windows - to fit you have to remove a strut and cut a huge hole in the side panels
3) An Alipne light is this narrow window, not essential but helps add some more daylight, they don't open
4)The side benches fold up once the cushio has been removed, for a tiny amount of extra load space
5) Full view of the side bench with both cushions and the waist belts
For the options on seats and fabrics then you can see all the options of seat design and fabrics here, my side benches are the same fabric as the front seats,
http://www.exmoortrim.co.uk/
Mine also came with a dog guard that was standard with County spec cars back then, I only took it out as I knew I was going to carry people in the back and the mesh makes the back more like a cage!
County pack comes with alloy wheels, dog guard, radio /cd player, side steps, rear headlining, cloth seat facings, "proper" tyres not farmers' special narrow Avons!, rubber load space mat, driving lights (mine have long since been left scattered across Scottish forests!) and a pop-up sunroof (best avoided, not because they can leak and mine doesn't, but because in cold weather you get condensation on the join between the surround and the aluminium roof that drips icey cold drips down the back of your neck the first corner you go round or big bump you go over!)