On the song Two Of Us, from the Let It Be album, someone is heard whistling along with the song…………I always assumed it was John because sometimes John mocked Paul’s songs, and despite John’s intentions, the whistling was actually a good accompaniment to the song.

Um, what's the question?

LOL -
who did the whistling part at the end of the song - John or Paul (or George or Ringo)?

According to Wikipedia it was John and Paul:

http://en.wikipedia.org/wiki/Two_of_...eatles_song%29

Wasn't there a made for t.v. movie with this song title?

Yeah, it was about a 1976 one-day meeting between Lennon and McCartney. Came out in 2000.

Fictional, of course. The movie was about how they would start up their little band again. (This was around the time Saturday Night Live wanted the band to play on their show.)