Here you can see a spring compressor in action. This allows the nut that holds the assembly together to be safely undone. Warning! spring compressors have failed. It's wise to be careful at this point and to point the springs in a safe direction.

A deep ringspanner is needed to access the top nut that holds it all together. You can check what size is needed before starting the job by levering the plastic bung of the top of the suspension turret whilst it's still in the car