I booted into recovery mode to delete the update and stop the nag but forgot to turn wifi off. I feel like such a noob! I totally freaked out when I saw the progress bar appear thinking I had just made a huge, huge mistake. Thank goodness I've got a Cubic Nin cart and Ironhax 1.1 and don't care about future kernel hacks, so this won't actually affect me at all. But just to caution others to quadruple check you've turned wifi off before trying to delete the update