The back wall of my house was completely covered in ivy and we just pulled it from the bottom and it came away just like velcro. The surface of our wall was harled so perhaps that was why it was so easy, maybe on brickwork its different. Good luck with it.
I have been told that you should pull the ivy off the wall and it will come away mostly all together. The marks that are left, can be removed by rubbing the wall with a house brick.