Ahhahhh.
So if I just start with my video at 360 degrees and go backwards from there. That works
Not quite intuitive but it works.
Using the snaps in the preview (red dots) still only sets the rotation to a positive clockwise value - eg if I drag the snap ANTI-clockwise to -30 degrees it actually sets it to 330 degrees and then when the motion is played (animated) it rotates the clip CLOCKWISE from 0 round to +180 and then to 330 - when actually what I would want it to do is to rotate from 0 anticlockwise to -30 degrees (330 degrees).
I have a fix now that enables me to rotate anticlockwise - the only time I can see this fix causing an issue is if I have a single clip that I wanted to rotate from 0 to -180 (anticlockwise say) then back round to 0 clockwise and then round to positive 180 (clockwise). I think I could possibly do this by splitting the clip. The time will come soon when I need to do this so will see how I go.
Thanks for you help.