from your pics i would .personally, think twice about cutting out and
replacing the bricks that are close to the tiled roof ( third pic of
original post). I would be afraid that they might disrupt the return on
the render of the underside of the roof slate/ tiles and adjoining
bricks as they are close to the end of the courses of brick..If it were
me i would just reface these as they don't seem that bad. As they are
high up I don't think anyone would notice any mis matching , although I
think it would be important to keep the brick line. If it were me like
i would make up the brick faces, let em go off a bit , cut too size-
let em dry and then repoint as if they were the original bricks,. The
refacing of the bricks would be done with cement dye to try and match
colour, as with the pointing.
I am not a professional so its just my opinon.