Spoke to them and I have to say that whilst their computer system appears mildly useless, their service reps are very helpful and willing.
They don't think that the extra length will make any noticable difference, but they are sending me another pair after double checking they are identical to each other! He thought that the length difference might be on an offroad variation or similar which isn't availabe here.
Thanks for your help
If anyone is tackling a fork overhaul job on a YBR or similar, I would be more than happy to share my experience, so please send me a pm!
Chris