question for the english/british?

We don't go around calling each other mate all the time.

However, "You what?" is often used in informal speech to request that the addressee repeat their utterance.

We are just as likely to say "eh?", "what?" , "pardon?", "Say again" or more formally, "Would you repeat that please".

Similarly, "You're having a laugh" is synonymous with "You must be joking" an informal way of expressing disbelief or dismay. Other similar expressions include

"Are you taking the pi**?"

"Pull the other one. It's got bells on it"

"In your dreams"

"You can't be serious"

"I don't believe it"

I, personally, never say"you wot mate?" or "are you avin a giggle mate!?" but they are sometimes said; it depends where you are from, what your background is, and who you are talking to.

An upper class English person is not going to say these terms. A middle class person may say it as a joke. A working class person may say it as a joke or as the intended phrase.

These kinds of terms you will never hear at a business meeting, you might hear it with friends down the pub though.

I'm British and I can honestly say I've never seen nor heard them before.

I don't know where you see that, but I promise it's not a common thing with most of the population. So no, I wouldn't say it. They would probably think of you as a joke, haha.

Only certain accents in England say the first one, but I have never the heard the second one? I guess it is jokey most of the time, and is never used in arguments unless you are intimadeting someone. It does depend on which part of England you are from, mostly Geordie, and maybe the background of you and your parents 😊

Oh yes