I have a friend from Nottingham. None of his family has ever lived in that part of London, let alone London as a whole. But he grew up watching UK shows with cockney slang being used, mainly Only Fools and Horses. That's led to him using it often in his everyday speech. E.g. he'd say something like "I had a butchers in the shop the other day for something good to eat, no luck though". I personally don't see it as weird and I'm more neutral towards it, but some others in our friend group think it seems inauthentic and a bit silly, if not weird, that he's using the language of a region despite never living there. What do you think?

Edit: So from the comments, I've gathered that my other mates are just a bunch of plonkers and it's spread to most of the UK; it's pretty much normal. Thanks.