Removal of Door Cards
There is another guide on here about this procedure under the title:
How to fit rear speakers! by 1.8stilo so please follow this - please note you have to remove the rear seatbelt which holds the door card in place and this is a 17mm bolt and it is tight especialy the older your car is

If you find the bolt reluctant to unscrew don't force it because it will snap as i found out :bang:, spray some WD40 or other suitable lub on the bolt thread, screw it back in leave it a few moments then unscrew again, repeat procedure until bolt is removed.