mate, i used to work for halfords
halfords roofbars are the old thule make, if your local store knows anything, which it probably doesnt, they can ring thule and replace part free of charge
you really should ask...and they really should know
i went on a training course with thule when i was there and he said this isnt a problem
even if they cant get it for free, its not gonna be that much. get them to ring thule