Apologies, "not working", bad choice of words.
I actually think the TM has nothing to do with it now.
I apply the TM to a loaded Bitmap which it then happily transforms perfectly.
The issue I'm having is if I reset the app I'm building and load in another Bitmap it retains all of the previous transformations.
I thought if I removed the target & then destroyed the TM that would reset things.
I now think that I need to reset the dimensions & positioning of the container clip.