Go on the door card removal guide, just above the door card theres a tweeter, that jsut comes off with the door card, theres 3 torx bolts behind there, undo them and pull the mirror off. Easy.
 
easy enough, did it on my last ibiza

remove door card, remove the bit where tweeter is, undo three screws and then you can see what's what from there ;)

then put back together