A short BBC story:
The first breakthrough in the battle to crack Nazi Germany's Enigma code was made not in Bletchley Park but in Warsaw.
Link:http://www.bbc.co.uk/news/magazine-28167071

GCHQ's Director at the Polish ceremony said:
What happened here in 1939 changed the course of history and we are here to honour those who are responsible.
We owe the Poles a great debt for their work and decision to share their knowledge as war loomed with France and Great Britain. Curiously two of the Poles fled to France, after May 1940 worked in Vichy France before fleeing to Spain in late 1942 and then to England. Their French partners did not escape when Vichy fell and throughout their captivity stayed silent.