T i m wrote:
Now, am I supposed to add a waterproofer to the mortar mix for that
area or will plain motar be ok? (this is a single 4 1/2" brick wall,
rendered on the inside and the dpc is only about 1 brick course above
the surrounding hard standing).

Chuck some waterproofer in (read the instructions, it's *not*
good for your skin, and makes the mix smell of pss) and make
a wide weatherstruck joint over the DPC. If you haven't damp
problems now, the "1 course above level" isn't an issue.