I don't say it's like the Focus itself but with that if you removed the trim panel on the inside of the door where the mirror was then it was held on with one or peraps three 10mm headed bolts that just undid. You may well need a longish and thin socket to be able to get at the bolt head due to it being behind the metalwork of the interior of the door.
I'll check the TIS disc as well to confirm
I'll check the TIS disc as well to confirm