Looking at aerial imagery of Norwich (Link) it appear to have structures in two corners that provide access to the battlements.  These structures are not seen in photos from the ground (Link) (The closest corner with the flag is one of the covered corners.  Photos from on the battlements (Link) make the merlons? (wall sections) seem taller than is often seen, extending up high enough to make the covered corners blend in with the rest of the wall when seen from ground level. 

Falaise does not appear to have covered corners the same way, although do not know enough of the history of either structure to tell you which is more historically accurate.

Depending on the size of your planned build, those covered corners might be a challenge, but hopefully you'll post pictures of it along the way for the rest of us to draw inspiration from.

Mark