Tannoy Canterbury GR Placement in a 23' x 34' room with 12.5' ceiling

That is a generously sized room. I'd put them about 6'8" out into the room on the short wall, eight or nine feet apart. Sit about eight or nine feet away from the center point between the two speakers. Toe them in so that the tweeters cross just behind your head in the listening chair.

This set-up will give your Canterbury's plenty of breathing room. Allow the speakers plenty of time for break-in if they are brand new. They don't sound good at first. But they will take your breath away in short order.

Congratulations! 

keith, pick up a copy of Jim Smith's book, "Get Better Sound".  Not only is that instructive for placing any loudspeaker, Jim personally owns Canterburys now.

I want to thank everyone for their input!  Long wall, short wall, hard to tell where to start.  I ordered the book "Get better sound" and will just have to experiment.  I think I will order some casters for the canterburys so as to make them a little easier to move around until I can narrow down placement.  At least this will make quick worker of where NOT to place them!
Keith