If the ivy is dead and stripped off what is left are the roots. I have come across two types so far...ones that look like little suckers and ones that look like millipedes!
The millipede ones are easier to get off ....the suckers are lilltle suckers!!!!! But I agreee with my illustrious colleague, as hot water as you can get it and a lance...my turbo lance began to peel off the brickwork aswell so stick to a nornal lance ...it takes longer but a better result.