It's not free, but eBooks.com has a 20% Discount for Rosetta Books extending to the 31st of July. "Use the coupon code Rosettareadscp at the payment details page to claim your discount on any Rosetta eBooks."
They have the first 3 Vols. and the 6th of Churchill's 6-Vol The Second World War for $7.99 ea. (all Rosetta publications).
The Gathering Storm,
http://www.ebooks.com/ebooks/book_di...asp?iid=137264
Their Finest Hour,
http://www.ebooks.com/ebooks/book_di...asp?IID=161701
The Grand Alliance,
http://www.ebooks.com/ebooks/book_di...asp?IID=155801
Triumph and Tragedy,
http://www.ebooks.com/ebooks/book_di...asp?IID=137274
A bit less than Fictionwise.com's per volume $6.45.