Take It Or Leave It is, as the sub-title will tell you, The Madness Movie and it essentially just shows the band members working (failing) at a variety of days jobs and going through lineup changes until about midway through the movie when the focus switches to showing their first few shows together and ends (I'd say "spoiler" but, seriously, that's just silly) with them backstage "Now" (about thirty years ago "Now," but still) waiting to go on to a sold out crowd because they've become quite famous and popular.
The whole movie sort of has a documentary feel but I'm pretty sure that last scene is the only one in the movie that isn't staged.
Overall I liked Take It Or Leave it but it took me a long time to decide I wasn't bored; the whole thing is sort of quiet and meandering and in a weird way it reminded me a lot of Filth And Wisdom, what with it being about struggling musicians and all.
But where Filth And Wisdom was clearly a movie-movie (complete with a plot you don't really care about and a spine-melting movie-ending kiss that is glorious until you remember that no matter how long you live Eugene Hutz will never kiss you like that ever), Take It Or Leave It is less cohesive and more of a ... I don't know. A fake documentary, I guess, but not of the This Is Spinal Tap variety and not of the Forgotten Silver variety, either.
It's more like Madness figured "Well, we're famous now; maybe we ought to show people how we got here. And let's rip the lid off a lorry while we're at it." So that's what they did.
At least that's how it seems to me. If you really want to know for certain, I guess you had better ask them.
End of line.