You’re correct Dave that “and” vav is pronounced “u” before labial consonants. More precisely, “and” vav is pronounced “u” before “Bamuf”, which are words starting with במופ, that third one being a vav.
“And” vav is also pronounced “u” before words starting with a shwa.
However in that last rule, if the schwa is on a yod, the vav is pronounced vi. An example is “and Jerusalem”, which is vi-rushalayim.