Originally Posted by
Aviatrix
The UK is fairly unique in Europe in still having separate titles for married and unmarried women - most of the rest of Europe abolished that distinction decades ago, and rightly so. (Why should there be a Fräulein when there is no Herrlein?). I'm sure I've been to airline booking web sites where there was only one choice of title for women, either Mrs or Ms.
So... very much a non-issue!!!
the correct default usage is indeed
Ms in any situation.
In a business context it would be discrimination to ask between Miss or Mrs. But a customer may pick one as a personal preference.
Most younger people, male or female, don't use any honorific. Even doctors have a tendency not to use Dr. beyond work or by using more defined post-nominal letters.
The usage is by older generations, if someone has always used Miss or Mrs, they may prefer to keep using it. But, the historic usage was [stupidly] to call the woman by her husband's name e.g. Mrs John Smith!