Hello, I'm a Nigerian(proud) who's been privileged some time overseas, especially the UK where I've lived a while studying the British Language and Culture in general.

If you intend visiting the UK, there are common informal words/phrases spoken by the British that might sound somewhat strange to you - but no worries, here are some meanings below:

Are you alright? - it's a popular greeting that means 'Are you okay?'. Common responses are Yes I'm alright, you? or Not bad at all, how about you?

*Note: They don't mean you are insane or anything by the question.

Hey Mate! - 'mate' means friend/pal in Britain. So this means 'Hello Friend'.

*Note: They don't mean you are their age mates, hence you shouldn't be offended by this. It's just their friendly way of saying hello.

What do you reckon? - reckon means 'think' in this context. They actually mean 'What do you think?'

*Note: However, Do you reckon a trip to Nigeria means 'Do you fancy a trip to Nigeria'

Be in my office about half-twelve - would mean 'Be in my office half past twelve (12:30) '

*Note: Half-three means 3:30 and so on.

Do you fancy the South African lecturer? - would mean 'Do you like the South African lecturer?'

*Note: 'Fancy' here could also mean 'Are you attracted to the South African lecturer?'

Can you spare a ffag please? - ffag implies 'cigarette'. This would mean 'Can you spare a cigarette'

Take out the rubbish - would mean 'Take out the trash/waste bin'

Can I have a cuppa - 'cuppa' means a cup of tea/coffee.

I'm in a flight tomorrow - would mean 'My flight is tomorrow'

Don't take the piss out of me - 'Don't take advantage of me'

There are many popular phrases and idioms used in Britain, but will leave it here for now.

Do you know any?

It does not sound completely strange. Even a kid would easily decipher those phrases.

You're right, have heard couple of it in movies

You're right, have heard couple of it in movies,but it's informal

MrMann1:
It does not sound completely strange. Even a kid would easily decipher those phrases.

Yeah kinda true, but to few others who don't.

I want celtic phrases, and I want them now. Give me celtic phrases right now!

RickRichards:
I want celtic phrases, and I want them now. Give me celtic phrases right now!

Haha be easy mate. Feel free teaching us if you know some.