First thing, take off the wheel.

Next, you'll need to take off the plastic strut cover inside the car:

This should just pop off, as it has two locator lugs on one side, and a pair of internal clips on the other. Prising it loose carefully using a screwdriver is easy, or in some cases you can just use your hands.

When you've taken the cover off, you can then access the top nuts which secure the suspension support. They'll need a 12mm spanner to remove. I used a socket myself, much easier to access them, and they are only torqued to 68Nm. 

The bottom end of the shock absorber has a circular section through which the bottom securing bolt goes through. This bolt is quite tight, being torqued to 103Nm, and will take some effort to remove. Nothing a little bit of muscle won't fix. You'll need a 14mm spanner for this, and make sure it's good quality!

The below image is a close-up of the bolt: 

Underneath the axle, you should put something to support it, in my case, I used a couple of bricks with a red rag to cushion the axle. This stops it moving too far, especially if you do both sides at the once.

Having removed the bottom bolt and top nuts, you can then remove the assembly which includes the spring and shock absorber. In my case I discovered that the shock absorber was still a standard unit, and likewise, it would appear, the spring. A picture of the Koni units against one of the stock ones is shown below: 

Installation is simply the reverse process. If you don't have a torque wrench, then you should have an idea of how tight the nuts should be from how much effort was required to remove them.

The rear suspension doesn't need re-aligning as there are no adjustable components in this case. If you've had a rear suspension cut, with independent rear suspension installed, then it's a different kettle of fish, and outside the scope of this article.

Below are two pictures of the finished product, you'll notice the different in stance between the front (not yet done) and the back: