The brief, I believe, was to aim for Cyprus after dropping the nukes, where hopefully tankers would be waiting if needed. There would have been no AAR out of UK. Incidentally, the '15 tankers' gig was to get a Vulcan the 4000 miles from Ascension to the Falklands with enough fuel on board to make the return trip. It does not reflect the Cold War situation. Bear in mind also that the Vulcan's main weapon was the Blue Steel stand-off missile, which would have been launched a few hundred miles from the target.