My wife’s English is very good. Nevertheless, on our last trip to the UK I found myself having to translate and explain a little more than usual, words like “grockel” (tourist), “twappy” (soft or floppy) and “vake” (sulk) being new to her. This is not surprising, however, as they’d be unfamiliar to most native speakers too. They’re all Devonshire dialect
Growing up in Exeter I was familiar with these (and many other) terms, and had a vague awareness that people in other parts of the country didn’t use them, but it wasn’t until I visited Genoa that I got a sense of how strong regional differences could be, not only in linguistic but also cultural terms. Genoese, like most Italian regional dialects, is incomprehensible to anyone from another region, and has a rich heritage of jokes, poetry and song. Renowned singer-songwriter Fabrizio De André wrote a whole album in Genoese, yet it’s hard to imagine anyone doing this with West Country dialect.
Regional accents have become much more publicly acceptable (even a source of pride) in recent years, as can be seen by their increasing audibility in the mass media. I can remember a time when all the voices I heard on the BBC spoke RP. Nowadays newsreaders use their native their Welsh, Scots, Newcastle or Yorkshire accents with no shame or fear of mockery. However it’s interesting to note that some accents will probably never be considered “cool”. These tend to be accents associated with farmers and rural communities (i.e. East Anglia and the South West). Devonshire “yokels” are seen as the British equivalent of “hillbillies”. 
My own accent softened while I was at school, and can now only be heard occasionally in certain sounds (a more audible ‘r’ at the end of words, for example) when I’m back in Exeter with my family. I love to hear it (although some regional UK accents, like those found in the North East, are extremely difficult for me to understand), as it adds colour and regional specificity – I know exactly where I am when someone calls me “my luvver”…