Thanks guys.
Presumably with the cant brinks, they have to be set into the existing vertical wall above it, which would involve chopping out some of the existing brick.
I think that I will go for the rake and repoint and then build up a 45 degree slope with the mortar.
We have a chimney breast that sticks out [roud from the end wall. It is narrow most of the wy up, but from the bottom to about two thirds of the way it is wider. From wide to narrow it is stepped in by bout half a brick each side over 5 courses or so. THe steps are flat brick.
I think that...