Okay I may have found a solution. It seems however that it is the long way round...
Rather than use a uniform fill for the cut surfaces, I have changed it to cut fill - as in settings.
As a result the brick surface showed the cut fill as long lines diagonally through the cut. To change this I used Options> Element Attributes> Building Materials> Brick, and changed the fill type to foreground - entirely black.
This seems like a workaround rather than a simple solution as I feel archicad should not incorporate fully, without option, sun effects into the 2D documents. Not everyone wants a document affected by a sun environment.
Thanks again for any future enlightenments on this topic, I think it could do with being reviewed and solved - a quicker, less invasive solution.