Would be a shame to miss the return over the devils staircase even though I know it is a pretty grim thought when you are tucking into chips and beer in kll. Cycling the road should be your last resort as I have seen members of the group going that way and getting back to car in about the same time.
Bus from kll is a local running to ft William don’t think there is one going toward kh.
You could always try breaking the bike down and wrapping in the black bags and tape you have with you to make them into “hand luggage”