So I was rather well, shocked and appaled? haha to see it being used in dr who last week !! Not in a convo between 15 year olds hanging in the streets, but by the dr herself !! So no idea how prevalent it is in real life in the UK but you certainly could have heard about it.
Edit: there is even a wikia entry about it. https://tardis.fandom.com/wiki/Fam (had to check if I wasnt seeing/hearing things haha)