Out of curiosity, after watching a very interesting show called Hungry Boys on channel 4 I decided to watch the post-show chat on channel4.com/hungryboys ... It proved quite incisive:
The show was good fun, but it was obviously pre-arranged and heavily set up. But according to Tim from the show, they appear to have been random members of the public who emailed in to channel 4 (perhaps with a few contacts that may have helped)
River Cottage was obviously the strand they used to give it a strengthened identity. And due to it's prime time slot I presume Hugh Fearnley-Whittingstall provides a VO with occasional dubious interaction via text to add to the River Cottage theme.