Another question for the Brits on the list

[Carol]

I'm editing a manuscript by a non-native English speaker who wants to
use British English but is making lots of errors, one of which is
referring to an unmarried teacher as Mrs Somebody. (Sctually she
spells it the American way, "Mrs."). I'm wondering whether British
English uses "Ms" or whether unmarried women are always referred to as
"Miss," as they were in the U.S. before feminism came along.

Carol, who should have posted her request this morning and hopes to
get some quick, authoritative answers!