Symptoms:
Rear wiper stuttering, noticeably slower in its sweep, unable to park itself, ultimately not working.
Time:
Rear panel and wiper mechanism removal: 5 mins
Rear wiper mechanism disassembly: 15 mins
Rear wiper mechanism repair and reassembly: 10 mins
Rear panel reinstallation: 5mins
Tools:
Trim removal tools
13mm socket
10mm socket
Wire brush
Grease (Silicon and white-lithium, in my case.)
Tape (Self-amalgamating is the best option, due to water resistance)
Superglue
Process:
1: The first step is to remove the rear wiper arm, 1x 13mm nut and then gently pull the arm off. If your arm is seized and you do not own any pullers, channel pliers are a great budget option. Place one jaw on the backside of the arm, and the other jaw on the top of the exposed wiper spindle, then squeeze. With the wiper arm removed, open the boot and remove the hatch panel. There are a lot of guides for this, see Roberts as an example.
2: With the hatch panel removed, undo the 3x 10mm bolts securing the rear wiper mechanism to release it and remove from the car. There is a plastic sleeve that goes over the aluminium casting of the mechanism. Ensure this is removed too as it forms part of the repair.
3: Use your wire brush to clean up the corrosion on the aluminium casting surrounding the wiper spindle. This should expose a C-clip and washer, which are located on the spindle in a groove. Remove the C-clip and washer, putting safely to one side.
Corrosion buildup
Spindle C-clip
Spindle washer 4: Flip the mechanism over, and undo the 10mm nut on the back of the motor output shaft, taking note of the orientation of the linkage arm. Put the nut and the washer located beneath it to one side, and undo the 3x 10mm bolts securing the motor to the aluminium casting. Place these bolts and their washes to one side, and let the motor drop away from the casting.
Linkage orientation and motor bolts 
Motor removed5: Using penetrating fluid of your choice, and lots of elbow grease, pull the linkage arm and attached spindle down away from the casting. Rotating the casting as you apply downward pressure will aid in removal. This is the most time consuming, and most challenging, part of the repair. Note, the more 'seized' your mechanism is the harder this will be. I'd advise doing this as early as possible once you start noticing symptoms, or perhaps even doing it preventatively.
6: Once linkage arm and spindle have been separated from the casting, you should see a buildup of corrosion on both the spindle and the inner bore of the casting. Clean these up however you please, I used scotchbrite, parts cleaner, and metal polish.
Casting inner bore dirt
Spindle dirt 7: Apply grease to the spindle and inner bore of the casting and mate the two again. If sufficiently cleaned up you should find they slide in with minimal pressure and the linkage is then able to rotate very freely. This is what you are looking for. I used white lithum grease here as it is water resistant and excellent in metal-to-metal environments. Place the washer and C-clip back to secure the spindle in the correct place.
Cleaned spindle
Re-installed spindle and C-clip 8: Flip the mechanism and casting over, re-install the motor, and the secure the linkage arm to the output shaft with the washer and 10mm nut.
9: It's now time to turn your attention to the plastic sleeve that goes over the aluminium casting. Clean out any corrosion present in the sleeve, and if required superglue the sleeve back together. Apply self-amalgamating tape to the exterior of the sleeve to restore its structural integrity and water-resistivity.
Plastic sleeve 
Repaired sleeve 10: Grease the inner bore of the plastic sleeve and slide over the casting. Grease here will reduce corrosion on the casting and help to prevent water ingress down between spindle and the casting bore. I use silicon grease due its water resistance, and ability to help swell the rubber o-rings in the window. The plastic sleeve has a cutout and the casting has a protrusion to help you orient it correctly.
11: Reinstall in the car, check operation before finalising the installation by relocating it in its place. Refit the hatch panel, and secure the wiper arm.
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