As you might be aware, for some reason the UK is pondering mottoes/catchphrases ... a semi-tongue-in-cheek piece in the Times ends with this suggested motto for Birmingham:

Philip Howard, the classicist of The Times, has helped me to translate it into Latin, and the five-word motto would be splendid, in fact, for Britain itself - except that it undermines the whole Brownite constitutional project.

Ne nostra in fundamenta subeamus: “Let us not climb up our own bottoms.”

FWIW and all that ...