What phrase does "Right" mean in British speech?

Just an interjection. Sort of like OK, or Well, or So .... "OK, today we are having a visitor so you all be on your best behavior" might be something you would hear in the US, but in England, you would more likely hear "Right, we have a visitor today etc."

Kind of a way to reset the conversation into the direction the person wants it to go. Doesn't really "mean" anything. Just a verbal signpost of sorts, sometimes used to get attention, sometimes used to change the subject, sometimes just out of habit. Lots of words and short phrases in English that are like that, that don't mean ANYTHING, but get said all the same. You know?

It is sometimes used as an emphasis or to gain attention. 'Right'! 'Today we are studying dinosaurs'.

It is a manner of speaking rather than correct grammar. It can also be used instead of 'Correct' in answer to a question. 'He gave the right answer'.

a statement or piece of information that is right is correct and based on true facts

if you are right, you have said something that is correct and based on true facts

the right thing, person, method etc is the one that is most suitable or effective

http://www.ldoceonline.com/dictionary/right

http://dictionary.cambridge.org/dictionary/english...

http://www.oxfordlearnersdictionaries.com/definiti...

It is used the same as Americans use so or OK to begin a sentence.

https://www.collinsdictionary.com/dictionary/engli...

"Listen up"