@djjd62,
I went on holiday to Houston, and stayed with a friend who worked at the British consulate. I'm from the South of England, and my accent would be described as 'Estuary English,' not that difficult to understand. I didn't have any problems in the city, but when I went out to the countryside they had real problems understanding me. My mate, who had been there a while didn't have the same problems. When we stopped off in a diner half way to Austin, the waitresses spoke to my mate, instead of me, even when they were talking to me, expecting him to translate, but I could understand every word they were saying. They just couldn't understand me.
Later on I watched an episode of Eastenders (A British soap opera) on Texan public tv. It was only then, after spending time listening to Texans talk that I realised how much less we enunciate our words, how much we use the glottal stop, and run things together. In the end I had to speak in a really posh accent, because that's how they expected me to talk, and that way I was understood. I've never had to do that anywhere else, and it was hard work, almost like playing a character in a play, a posh version of myself.
In most forms of mainland English the 'ugh' sound is used extensively. It's probably the most common vowel sound. That's not the case in America where you tend to sound most of the letters. A wierd example is Tottenham, most Americans say it as it looks. We say Tott 'nam. But really we don't, we actually say Tot 'en 'am, but we run it together so quickly it sounds like Tott 'nam.
Anyway my point is, is that if someone like me, with a rather mild accent had such problems being understood, (admittedly only in rural Texas) what chance has Cheryl Cole got.