On the part of the north wall attached to the east wall is the jamb of one of the lower windows of the same date as the east window.  
ppa61f1b25.jpg
Reconstruction of the window mentioned above by
Stuart Harrison,
Ryedale Archeological Services, 2008
The east window, part 3
The wall probably had 5 such windows, 1 for each bay.

In an angle each side of the arch is a cut-away 4 foot vaulting-shaft (H79), apparently for the insertion of an image and its niche (WARD).