There is something that doesn't quite add up here. What could these Polish codebreakers hope to achieve for victory over the Nazis and the liberation of Poland (OK, we now know what that led to but they didn't then) by remaining in occupied Europe? These were very intelligent people who knew full well that little other than minor tactical success by the French Resistance could be achieved by breaking Enigma for them in Vichy or in Occupied France. Of course, they wouldn't know what progress the British were making with Enigma, but whatever it was it could lead there to strategic successes that in turn could lead to final victory.
Was there an issue vis a vis them and the British? Had they decided we had betrayed them? If so, why didn't they feel the same about the French? Were they simply trapped there, with any attempt at escape (via the Pyrenees?) courting the danger of being captured and interrogated? Why hadn't we managed to persuade them to join us from the very start? Were the French hanging onto them simply to deny them to us? Unthinkable that one of course. Sorry!
Franek, can you help?