Hi SC,
Thanks for the comments - just to make sure, I've tried it again with only the xbox pad plugged in, and in yaw mode, everything is correct as per your comments.
If I then switch the game pad to roll instead of yaw (by clicking in the left stick), then it feels reversed - but that's at least a comparison between what happens if I were to press the left arrow key, followed by pushing the stick left.
At least I know I can use the pad properly to yaw, and if I need to do a roll, I'm able to use the keyboard properly..
Thanks again...