Hi,

Can anyone offer advice on the easiest way to replace the rear wiper blade? Looks impossible with it hidden away in the spoiler and it always self parks.

You basically have to turn it on and turn off the engine when it's in the vertical position, took me a few times to get it right.

As Peter says, turn the engine run switch off when it’s pointing straight down. 
You don’t actually have to have the engine running to do it though, you might flatten the battery if you start the engine to many times. 
Just press the start button twice without touching the brake pedal, operate rear wiper, press start button when wiper points downwards. 

Many thanks.