France and England Supported Soviet Possession of W. Ukraine, W. Belorussia

France and England never demanded that the USSR withdraw its troops from what had been Eastern Poland.

On the contrary; Ivan Maisky, Soviet Plenipotentiary to Great Britain, wrote to his government on October 17 and again on October 27, 1937, that the British representatives – on October 27 it was Sir Horace Wilson, P.M. Chamberlain’s main advisor – would never demand the return of the Western Ukraine and Belorussia to a restored Polish state but would insist on borders “on its ethnic basis.”

The following documents are in the series "Documents of Foreign Policy of the USSR", published during Eltsin's period. The full bibliographical information is in Russian at the top of each page. For the full documents in PDF format, click here for the October 17 document, here for the October 27 document.

Here's an English translation of the headers and the parts I've highlighted in the boxes.

1. 695. Telegram from the Plenipotentiary Representative of the USSR to Great Britain I. M. Maisky to the People's Commissariat for Foreign Affairs of the USSR. October 17, 1939. Special. Top Secret.

I breakfasted today with a colleague of the Minister of Foreign Affairs Butler. From the conversation with him I note the following...

2. Poland. Butler related that Zalesski*, who had recently arrived in London, did not demand the return to "a future Poland" of the Western Ukraine and Western Belorussia ... According to Butler's words, English governmental circles consider that there cannot be any question of the return of Western Ukraine and Western Belorussia to Poland.

(* Minister of Foreign Affairs in the Polish government in exile.)

2. 731. Telegram from the Plenipotentiary Representative of the USSR to Great Britain I. M. Maisky to the People's Commissariat for Foreign Affairs of the USSR. October 27, 1939. Immediate. Top Secret.

1. I breakfasted with the chief advisor of Chamberlain (and de facto the person who directs his foreign policy), the well-known Horace Wilson. ...

2. Most characteristic was Wilson's views concerning the desirable -- from his point of view -- outlines of a future peace treaty that must be concluded after a more or less lengthy war... Poland must be re-established as an independent state on its ethnographical base, but without Western Ukraine and Western Belorussia.