So, I'm from South Yorkshire, a county in the U.K. - this is a famous advert from 1974 (though I remember it from when I was small in the early nineties).
Everyone in Yorkshire talks like that, without deviation. They also work very hard down the coal mines, and in the steel factories. We all live in cottages and have pebbled streets. We also always have music by the famous Yorkist composer, Antonín Dvoák playing in the background wherever we go.
According to the text, the ad was directed by Ridley Scott, the guy who went on to film 'Aliens' .
I'll get round to it...my accent is actually more academic 'Yorkshire' rather than the more common street variety...but it's not as though I listen to motivational tapes with my voice on them before I go to sleep or anything - I don't really know how my voice compares.