My house has 2 extra DPC at 8ft and 20ft. The 20 ft one is being removed.
The 8ft one is sitting on a sandstone ledge that runs around the house. Looking at the DPC it appears to be attatched to the inner block wall, runs down the block, goes across the cavity gap and sits under the blocks that are directly above the ledge.
If like this all the way round it will prevent air circulation, it will hold water/condensation and there are gaps between the insulation. The vertical bed joints where mortar has fell off leaving gaps I can see through the gap. There is no mortar on the full width of the block. It`s as though they were pointed only, so mortar only on the first inch or so of the vertical bed joint. Lots of mortar crumbling away and rubs away with my finger.