A Brit' here, most British dialects are heavy on the R's. Whether that's the rural accents ranging from the Cornish (south west) to Norfolk (south east). Then you have the harsher sounding dialects of the north east - who also seem quite rhotic (or at least, the thicker accents are). Then you have the Welsh and -as mentioned in the article- the Scottish and Irish who all also emphasise their R's (it's quite amusing when I hang out with some of my Scottish friends as they can't pronounce "Karl", so every time they call his name, my other friend "Carol" answers!)

The ironic thing is, the way the English are perceived to speak isn't the way how 99% of English (let alone British) people speak. Even in London and it's overspills (the neighbouring counties), which is where our dialects are the least rhotic, most people don't pronounce themselves in the same way as they do in American TV. But I can understand why the stereotyped accent is used; it's a slower and more clearly spoken - which is ideal for broadcasting where the actor needs to be heard and understood by the audience. Many of the northern accents are spoken with such speed that it can be difficult for an untrained ear; even for some of us English! It's also a sexier dialect (few sane people would fall in love with a Geordie accent, Brummie or even Cockney, if they weren't already brought up in that area.

If anyone is interested, I'd be happy to find youtube videos for some of the more distinct dialects.

[edit]

Just been chatting to my wife about this. She's from the north east of England, I'm from the south. It seems I've overstated the amount of emphasis the north east places on their R's.

I'm not sure if I'm alone about this, but the funny thing about pronunciation is the moment you're asked to think about the way you pronounce a word, you've instantly forgotten how you normally talk!