Second attempt.

Longish - sorry.

        I wish I knew if it was my "Disputer" or Blip software playing sillibeggars.  
        I was about to say - Jerra came through yesterday , in lieu of Thur to help cut the Box - BUT - in truth, he did 90+% of it.
        How things change?  When we moved in the front "Garden" was wall to wall Grass with no Hedge/Wall - AND - if you look closely, you'll see two vertical "Cracks" near the screen centre.  That was the entrance to the "funnel" leading to steps up and a   B.    R.    O.   A.    D.    path to the Door. 
       Mate Bill kindly widened the Drive and used leftovers to close the steps access - SO - all the visible vegetation plus at least two small trees all came in the back of the Volvo.
        However - to the Boxes.  I've cut them, for decades, by Eye.  Considering the road slopes slightly up and the "Bricky" laid the Wall with a Spirit-level.  Not TOO bad, by Eye.
       Enter "The Hack" (WHY, with 6-7 different ways of using "Hack" - However there's another be en introduced) 
        This one was to lay a Ladder along the Wall top as a guide.  This was done, checked by Spirit-level, and found to be "true" despite appearances.
       The low Box is one of two I replanted in new position after closing Steps access (One died, one didn't)
        I/we also decided a year or some ago that converting the Buxus Cubes into a Box Hedge would vastly reduce work - THUS:-
       Instead of cutting
Back - Front - Left - Right - Top
we only cut
Back - Front - Top - One end.     The other end is against Al & Mary's wall.