I hate to disillusion everyone,but one of our Grandsons works for the production comapny that makes "Coach Trip"(amongst other programmes).
He tell me this.
The main coach is followed by a "back up" coach,that contains 2 to 3 pairs of replacement travellers.It also contains the film crew,productiuon team and any othe things necessary for the filming of "Coach Trip" that cannot be seen on film.
This is how the replacement couple can appear so
quickly,as they are "there" already!
However,the replacement passengers are not allowed to take part (obviously) in the main coach activities,they just stay in the hotel and entertain themselves.
I hope this is clear?