Thanks for the tips
By taking suggestions from both replies, i have come up with something that works for getting the rotation along the arbitrary axis. I found because I had already lost the local axes due to the earlier “Apply Scale/Rot” I needed to do the Shift V thing and also to use the script “Axis Orientation Copy”. It works but it is tedious to do more than once
Once I had essentially got the local axes back on my object I need to rotate, I animated 10 frames, works fine
Then I remember I needed to do the “Apply Scale/Rot” once more before I can export the file. But in doing this to my 10 frames it totally screws up the object position in the animation.
So I have got a conflict that I cant see a solution to, the rotation to be correct needs local axes, but the export needs the local axes to be reset to world axis by the “Apply Scale/Rot”.
I need to have a longer think about this or can anyone else throw in some ideas how to work around this conflict ?