I changed my surname by deed poll about two years ago to match DP and DD. It was just easier, quicker and cheaper than getting married, and I'm old fashioned in that I like the idea of us all having the same name. I also started calling myself "Ms", mainly because I didn't want to sound like DPs sister by using Miss (and also a "miss" with a child didn't seem right, I wanted to mark that I was now a full-grown woman) and also because "Mrs" would sound like we were married, which we aren't (yet).
Anyway, now I always give my name as Ms, but it tends to get filled in as Miss or Mrs by people over the phone, so I have ID with all three titles on.
I went to the Post Office to cash a cheque today and the woman behind the counter very nearly refused to do it, on the grounds that the cheque was made out to Miss X, and the letter I had as ID (from the same people, btw, god knows why it was different) was addressed to Ms X. The PO woman said "Miss would mean you have never been married, and Ms would mean you are divorced, which are you?" I said it was complicated, as I couldn't be bothered to go into my life story with some random woman. It was only through me having a big pile of ID of all different types for both titles that she "let me off" as she put it.
Surely it is my choice what title I decide to use?