Hi malpal,
This sounds exactly like a job I had to takle a couple of months ago, the ivy had grown up the garage wall and grown inside the roller shutter, causing it to jam up and it also got under the metal sheeting on the roof,causing leaks.
It was a dirty and dusty job, cutting it away bit by bit with secautres. I only wish I had some close fitting gogles at the time but was glad of my hat.
Any way once all the hard graft is out the way and you've cut it back to a foot or two from the ground, you could treat the cut ends of the ivy with one of the following products- 'Growing success ivy killer', 'SBK Brushwood killer' or 'Rootout'. Keep the stubbs covered with polythene and treat any other sprouts on sight.
I think you'l be glad to see the back of it. Good Luck Tbird+