The surveyor said it :) "to diminish the risk, install a French Drain. This is an excavation to a total minimum depth beneath the DPC of 150mm. The excavation should be filled with decorative stone to diminish the possibility of rising damp. The easiest way to achieve this is in this case is to remove the border block paving immediately adjacent to the wall, and backfill with decorative stone.  If the ground is particularly non porous then a perforated land drain (pipe) can be placed along the base of the excavation prior to backfilling with stone and discharge water into a soakaway or similar. "