Is there a way of pinning annotative text in one place whatever the scale.
I open different viewports at different scales and the text moves.

One way is to make sure that the justification of all instances (scales) of each instance of text is pinned to the same location, eg, BL=Bottom Left, etc.  It will probably take an extra step or two in order to do this efficiently.
JUSTIFYTEXT is probably going to be your best friend here.
 
Dave.

Thanks Dave,
 
Works a treat.