Addendum: A big hat tip to "Numerophile" who found the answer to #3:
Eileen Nearne, codename Agent Rose, was a wartime radio operator in the Wizard network in France. She died on 2 September in Torquay.The answer to 18-4 remains totally obscure.
Second addendum: Willofgod suggests "Angie Bowness. Sir Clive Sinclair married the beauty queen after 417 day engagment." I've seen this argued at another board, where they are trying to get confirmation on the 417 day period. Daily Mail story here.
Third addendum: The best answer seems to have been found by Robert Iain and Wireman:
"George John Patrick Dominic Townshend, 7th Marquess Townshend, succeeded to his peerage on 17 Nov 1921. On 2 March 2009, he became the longest ever holder of a peerage, surpassing the 13th Lord Sinclair (see below). He died on 23 April 2010, having held the peerage for 88 years, 157 days.(Previous post re the KWC quiz here).
From March 2, 2009 to April 23, 2010 is... 417 days.