Street said:I think its more a case of removing the mirror housing and taking that bit off the car.
I'll drop you a note with a guide
I think you could be right, I stripped it back as far as I could and I still couldn’t see a way of separating itZulu4 said:I think that black plastic part is plastic welded to a metal backplate and isn't easily separated from the rest of the mirror unit, even when the mirror has been removed from the car.

I’m way beyond that but thanksDr. Zed said:Pull off the tweeter speaker on the inside of the door and you'll see the release screws. You might also need to remove the door card to remove the lower one, can't remember. It definitely comes off relatively easily as I've taken mine off to respray it.
No problemDr. Zed said:Apologies mate. Re-read your post and you're looking how to separate the wing mirror from the black plastic bit. My bad. Rushed into answering!