Blair's A Journey sold 92,060 copies in its first four days on sale last week, according to Nielsen BookScan, (that was before turning up in in the pound shops).

At the time The Bookseller estimated that Margaret Thatcher's memoirs The Downing Street Years sold 120,000 copies in its first week on sale, (that was before turning up in in the pound shops).

- Source


then there are these:

Best selling Political Memoirs (selected) 1998 - 21st August 2010
(sales prior to turning up in in the pound shops)