I'm a Mr now

[Artemi]

Buying some (women's!) rugby tickets online of all things and the only available titles were Miss or Mrs
I'm married but kept my birth name and use Ms if I must (prefer either no title or a professional title but that's another thread).

I spent so long going back and forth between which to choose that finally in frustration I selected Mr.
Hopefully my obviously female first name means I won't get denied entry

I am a Mr too in these circumstances (definitely not a Miss or Mrs) or frankly when I feel like it because I don't think that Title should be an obligatory field anyway. Causes no end of very minor trouble, which I find amusing. Nothing actually detrimental has ever happened. Oh except my Dad opened some not very confidential post of mine once.

If I was booking something where correct interpretation of my sex from my chosen title was important, such as assignment into a single-sex hostel or ward or university room for example, or applying for a female-only job, then I'd go with Miss or Mrs and then complain vehemently. Or if bouncing a payment in either direction because of it would be very detrimental to me, although the bank doesn't seem bothered with titles these days.

my bastard ex’s hideous divorce solicitor always addresses me as Mrs Everything. So I address him as Miss Smith back.

Nicely done!

Once the divorce is dealt with, you can report them to SRA for this. Professional standards and that: sex discrimination. Well you can report now but I suspect that isn't the best choice for you.

I'm a "Lady" on Waitrose online site and I had a complaint that went a bit further than usual and got a phone call addressing me as Lady Redup.

Fortnum and Mason online, if I remember clearly, have Admirals, Baronesses, Princesses etc. That's good fun.

how is it not grammatically incorrect if it’s always done that way and is also taught to most kids in school to layout letters that way?

Because it's not grammar. Two nouns separated by a conjunction - it's fine either way. You can argue it's stylistically or conventionally correct, but it's not grammatically wrong to say Mrs and Mr.

If I was booking something where correct interpretation of my sex from my chosen title was important

...then I'd expect them to provide a box specifying sex. What if my title were Rev or Dr?

As a PP said, titles are rarely required these days. Just my name is fine and if you're being formal full name will do, like in "Am I speaking with Jane Smith?"

Whenever title is a required field on a form I just select the first option on the list. Rarely, it's ordered by alphabet and I'll be Dr but usually the default first option is Mr and so that is what I am. Including on bank accounts.

thats what I do too! I used a rather long military one for a particular shirt seller, and they obviously sold/have my name to another (furniture) company because they used my full military title… I complained and they said they hadn’t… must follow up on that one.