Remove the boot trim. This just has push fit clips, so you can pull them out without worrying about breaking them. I found it easier to remove the side panels first so I could see the clips.
Once the trim is removed, remove the plug from the washer motor
Remove the 3 nuts holding the motor on. The washers under the nuts are captive, so will remove with the nuts.
Open the top cover of the wiper and remove the nut holding the wiper onto the motor. The cover does come off if you need more access.
Remove the wiper. This requires quite a bit of force. I tried using a trim removal tool and it wasn't strong enough, so used a flathead screwdriver. Be careful of the glass and paintwork! I used an old teatowel as a buffer to stop scratches.
Pull the motor out through the bottom.
Remove the rubber washer from the hole.
Reinstall the nuts. This isn't necessary, but I prefer it as then I wont lose them. If you are reinstalling them, nip them up so the washers don't rattle. I used the kill all wipers kit, which came with a plastic bag and zip ties to cover the plug. I tucked in under the boot latch cable loop as shown.
Reinstall the nut on the motor washer. Again personal preference, I just like to keep it all together incase I need it in the future.
Clean the window around the hole, inside and out, as well as the inside edge of the hole. Mine had quite a lot of crap under the rubber washer. Using normal window cleaner for kitchens/bathrooms worked really well.
Test fit the plug. It doesn't take long, but make sure you're happy getting it centred in the hole. Apply the sealant to the plug flange and insert the plug.
Tape the back of the plug to hold in place, then fill the outside with sealant to ensure its waterproof. I used a wet wipe to get rid of the excess sealant from the glass. If you've ever used silicone sealant in a bathroom its exactly like that. Be careful when cleaning the excess that you don't push the plug out. I held the back all through this step just to make sure I kept it seated.
The sealant needed 1 hour to set prior to removing the tape, I left it about 3 to be sure. Remove the tape from the back and the film from the front.
Reinstall the boot trim, being sure to line up the clips with the holes before pushing them back in and you're done.