They seem frequent these days, but what were the first UK and Billboard Hot 100 number one singles with the F-word in the lyrics?

Songs like "Louie, Louie" and "Hey Jude" have non-lyrical background utterances.
"Kick out the Jams" by MC5 in 1969 has the MF-word as an introductory lyric but the single -- which hit 82 on the US Billboard -- was a censored version.
Jefferson Airplane's song "Volunteers" hit 65 on the US Billboard; the B side was "We Can Be Together", which has the word in its lyrics.

"Who Are You?" by The Who hit 14 on the U.S. Billboard and 18 on the U.K. OCC in 1978 is the first unequivocal example I could find of a single.
https://en.wikipedia.org/wiki/Who_Are_You_(The_Who_song)