Hi mate, go to your local ford supplier, and buy the round plug, and if you mark the triangle, then remove it any way you can, like making a hole and lever it off, and then when youve fixed the mirror on then use the new trim, ive had the problem as well, the more you try to prize the plug out, it closes any gap up.
Andrew Mckenna. andrew.mckenna1@ntlworld.com, April 2007