I just saw it again, and at somewhere between 2:00 and 3:00 (during the rehearsal) there's a man in the background who looks an awful lot like John Finnegan. Maybe it's really reaching, but could he have accompanied Peter Falk on the trip to England and ended up being in just a few seconds of the thing? (Probably just a coincidence, though.)

Nope. Just watched that entire scene and although there is a guy of his age, I do not think it is him.