You have to lever the whole winder away from the door. Its held on to a metal rod behind which has a groove running around its circumference, the winder has plastic clips which clip into this groove.
You should get something with two prongs, slide it behind the base of the winder, then lever it until it pops off. As i said before the Haynes manual says "Make up a fork shaped device" and shows a large flat fork with two prongs. I tried using a gardening fork but broke two of em
I use a large spanner wrapped in a towel to protect the soft plastics. Problem with this is you have to force the door card back but I'm affraid i don't have anything better.
Just protect the plastics as much as posible, one of my door cards has a small bit thats gone white where i've applied pressure and distorted it. Also remember which way they were facing before you took them off! They'll go back on any direction you fancy but you don't want it digging into your leg once its back together.
Hope this helps, if you've not already got them off good luck! They're tough bloody things. Once they're off, Have fun with the horrible grey adhesive which holds the door card on.