Why? I'm just a pigheaded, selfish, American male. I try not to be just another American who lumps the entire British Isles in as "British," but want to smack my fellow Americans when they tag Aussies and South Africans with the same.
Having a peppy mid-west US accent with some southern drawl on several words, I find the south of the English isle the easiest to understand, as well as Irish (the latter likely because of the make-up and settlement of the mid-west). More London and east England does have a sense of elegance, authority and flair that Americans especially enjoy in a model. Moving north, the Scottish women are also of an enticing breed of rising, initial tone in their speech that tends to cause American males to notice.
But the more northwest or west you move from London, the more Manchester or even Welsh I hear, the more it just totally turns me on. Not the men, and likely because it is far more difficult to understand for many Americans. But because those women, oh God that voice, as if it is English put into a foreign, yet erotic tone (from our standpoitn) that you can understand, but even enjoy struggling a bit to understand, almost seemingly softs-poken, but in a gentle way that flows well.
Even the vulgar comes out charming, almost as if the tone was designed for vulgarity with a pitch that commands well. A simple "Wank it!" from such a voice turns me to mush and sends me vertical at the same time. A couple of Lorna vids, with those curves, and that mouth flowing, oh God damn that gets me every, fucking time.