I recently had my dealer (Rybrook Warwick) take care of a ruddy great scuff I stuck on one of mine - £120+VAT, as I recall, which seemed to be a flat rate as it was the price quoted over the phone without any inspection of the damage. They did an excellent job; the only way you'd know anything had happened was if you really closely inspected the outer edge of the wheel and noticed it had a slightly squarer corner than the others.
That price might be at the higher end, to be fair; originally I intended to take it to a local place until my brother warned me off, saying they did an unsatisfactory job on one of his and were expensive at (I think) £150.