Instead of offsetting the original curve and moving its points back in, try generating the arcs from three points and only transforming the centre point.
thanks so much, really helps.
I was wondering if you can tell me how to duplicate on a slider (to duplicate it numberous times) so that it looks slightly like the photoshop image that I have attached.
also, could i just add, how can the arches move so that the mid point on the smallest arch would sit on the mid point on the last curve of the previosu batch. Not sure how clear that is but basicaaly as it is in the image.