If it's a discussion about the programme itself, then that'd be best in General Discussion.
If it's a discussion about particular issues that happen to be raised in the programme, then it's best that a new thread with an appropriate title is posted in whichever forum is most appropriate for the (perhaps this one).
The only one I can recall is
TV Alert:-The trouble with our trains (29/04) and it's not easy to search for ITV
Edit: I found the other one, it was a post advertising for people to take part in a documentary. We are happy to recieve requests as per our
forum rules "If you wish to advertise, promote or fundraise on the forum, you must first obtain permission by contacting us" and if a request is made it may well re-appear!
And, perhaps somewhat ironically, as this isn't a discussion about UK railways, this too will now be moved to General Discussion...