American here. I’ve always thought it rhymed with “hot”.
UK here, “hat”, but understand it’s sometimes pronounced differently.
*There was a young lady named Grace
Who said "If the whole human race
"Depends upon what
"The boys call a twat
“Then it’s put in a darned awkward place!”
First time I saw the word. Mispronounced it as rhyming with hot, but soon was corrected by various other occasions of British Pop Culture.
Another American, “…hot.”
And I NEVER thought of it as a Britishism. Even in the mid-80s, when I was around 14 years old, there was a stupid joke based on the word and on the then-airline TWA. Nothing British about it at all. (This was in the NY metro area, FWIW).
Nope, born & raised in the Detroit area. Hot has the same vowel sound as in father (hät), or an “ahhh” sound.
Hat is pronounced with your typical short-vowel ‘a-sound’. Like bat, sat, rat, or shat.
I’ve only heard twat pronounced in this area as twät. “My favorite band is Twathammer. They’re hot!”
Rhymes with hat. ‘Twot’ is also a word in my part of the UK though.
It more-or-less rhymes with “hot” for me in SA, but I’m familiar with the UK “hat” pronunciation and may use it for extra emphasis if around Brits.
I’m British. When I was twelve I had a hamster which somehow got nicknamed “Twottie”. It is only now that I am thinking :eek:
The 17th-century satirical poem “Vanity of Vanities” gives the British pronunciation,
*They talk’d of his having a Cardinall’s Hat
They’d send him as soon an Old Nun’s Twat *,
which was picked up by Robert Browning, who made the most embarrassing boner in literary history when he took it from that context to mean an article of nun’s clothing.
*Then owls and bats
Cowls and twats *…
but at least the British pronunciation was preserved. I guess this goes to show how much more easily the brain picks up the meter and rhyme of words than it does their meaning.
I’m from Aus, and twat rhymes with wanker.
Now, boner, there’s another word with varying connotations. 
I don’t think the non-sexual meaning is part of British English.
I used to date someone who pronounced hot as hust. Weird!
It depends which meaning is intended.
Rhymes with “hot” is the female body part.
Rhymes with “hat” is a wanker.
London/Essex/Anywhere-else-down-there.
UK, rhymes with “hat”. First time I heard it rhyme with “hot” was this scene from Easy A:
I had to go online to check what she’d said, which makes it amusing later on when she has to explains to her Parents what she said and, when they can’t think what the “T-Word” would be, she tells them it is “definitely slang, think British”:
Cunt?
Please.
No, they’re different sounds. I’m originally from Essex and now speak with an RP accent. Cunt is /kʌnt/ and can’t is /kɑ:nt/. The OED agrees with me, but I can’t link to it.
But it depends on your own accent’s pronunciation of “can’t”, doesn’t it?
To me (grew up in Warwickshire) they sound remarkably similar.
I read how in posh Estuary accents, the pronunciation of [æ] has recently been shifting to [ʌ]; e.g., hat pronounced like hut. An anecdote illustrating this:
A young lawyer working on an important case took the documents to a remote country retreat to work on them to be ready for court in London on Monday morning. The judge in charge of the case called to say he’d discovered that one more document was absolutely crucial but had been left behind in London. The lawyer said helpfully, “Fax it up, m’lord.” The judge said, “Yes, I’m afraid it does, quite.”
Who on earth asks someone to “fax it up”?