Any brickwork with lime mortar should be replaced with lime mortar.
The lime mortar is how the bricks "breath"
If you use cement mortar you'll seal in the moisture that's already in the bricks causing all sorts of damp problems, inside and out.
The damp bricks will freeze in the winter and the surface will "blow"
Next time you notice a blown wall on a house, take a look at the mortar. It will have more than likely been replaced by someone who didn't know what they were doing. Replaced with cement mortar when a lime mortar should have been used.
To advise otherwise is not a good idea, sorry.