It goes through the eldest bloodline. So it would be Charles, then William, then William’s children, then Harry, then Charles oldest sibling, (then through his oldest child and his heirs and so on)
Of course all the kings and queens of the Hanoverian line are usurpers. The rightful heir (on strict genealogical grounds) is a member of the Wittelsbach family of Bavaria. But since Culloden the adherents of the Stuarts seem to have thrown in the towel.