Hi!
As Tom said, Many Happy Returns is amazing for the fact that's it's silent for over 20 minutes -you couldn't do that now... or barely do that then!
I think that the two characters were part of the conspiracy, and the location revealed to Number 6 was possibly completely wrong. Or at least, a little of the way off - they couldn't let him know the actual place, if they were on the side of the village.
Also I find it interesting because, the characters of Cargill and Sinden were obviously British, but there is the angle of -was it the British government, or was it that these two men had changed sides, had defected? I love that angle because it shows that the village goes far and wide - can he trust anyone at all?