Honeybadgerx is right, the remedial work may not be as extensive as a full demolition and rebuild, but if I were you, I would want to know the worse-case cost to see if it is worthwhile proceeding (I.e. start spending money). It will also provide you with info to approach the seller to see if they will reduce the sale price accordingly. If in the interim, the engineers report comes back with a reduced scope of work, then your costs will reduce also.
Take the pictures from a few angles and also get on top of the wall to see if there are any tension cracks forming above the wall. These could be up to 5.2m away from the top of the wall (based on 12ft wall height).
EDIT: by this I mean cracks in the ground behind the wall, not in the wall itself.