I think that maybe Tim Minchin's solo work is better than his lyrics for other people--and more easily realized.
He uses too many words (to misquote Amadeus)--and not in a good way, the way Noel Coward or Stephen Sondheim or Cole Porter do when they're writing patter songs. (Or, even, the way some of the better hip-hop writers do.)
His clever ideas come too quickly and he doesn't seem to know enough about the specific vowel sounds and consonants that singers can use to make their songs understandable. Reading through Sondheim's books and interviews, he speaks a lot about writing lyrics that singers and actors can wrap their mouths around--and sometimes altering them for sing-ability.
If the actors can't make the lyrics mean something, then the song becomes about cleverness for the sake of cleverness--or, worse, the audience is left thinking, "I think that's clever but I can't understand what they're saying." At any rate, they're not connecting with the characters.
Perhaps the little girls are more understandable in London, but I don't think those lyrics, as written, help them.