Reached a point an hour or so ago where I figured I should go to bed… so glad I didn’t 
I decided that before trying to get the pawn to travel on a path between points, that it would be a good idea if I could atleast control its path, and in the process sort out the rotation being pawn local rather than world relative and I’ve managed just that! 
In the video below you can see me flying about. The left stick always behaves screen relative, i.e. push left and you go to the left of the screen, push right and go right, likewise for up and down. The right stick turns the pawn and the camera to simulate being constrained to a path. Whilst these turn speeds are the same, they are not bound to each other so I can move the camera separately to the pawn if desired.
Hopefully with the setup I now have it will be relatively easy to swap out the right stick values for one derived from the placement of markers within the world, but that will have to wait for another day!