I listed it as a TV Show because at 40 minutes it's not really a TV movie (even IMDB seems to list it as one) and it's only a one-off, not a series.

But is it a reality-show or kind of documentary, or a fictional story? In the later case it should be listed as TV movie.

Yes, it is fiction, it's a comedy done in the style of a TV documentary program. But it's only 40 minutes and it's not really a movie at all

As I've said before, "TV Show" is really too vague a category (it can mean anything that's made for television). We need new, more specific categories. I'd describe this as a "TV Special" (because it's only one episode) And why not just have categories for Reality TV series and Documentary series? Or just "Non-Fiction TV series".

"TV Show" category is mostly for Reality TV + Game Shows + Top-Gear-like shows. I do not know how to name it more properly. It is your language, I am open to suggestions
For this particular one, isn't Miniseries a good category? Even if there is only one episode...

Reality-TV would be a good alternative to TV-Shows. Maybe there could be a TV-Special or One-Off-Special category for things like this

That could be grouped with the series: it is a one-of made from a series

Why can't we just have TV Special? That would be the best description for this.

And we could just list reality TV shows etc. as "TV series" because they still are filmed as a series. But I get the feeling you want to seperate them from dramas and comedies. So how about "Non-Fiction TV series"?

Also I recommend a "Video" category for things like the Clarkson DVDs (because calling them "Documentaries" is a bit laughable)

By the way, I think "series" and "program" are British terms whereas Americans tend to say "show".