A recent survey featured in The Sun (and other sources) rates the Birmingham accent as the least "cool", and R.P. (Received Pronunciation) as the most "cool". I don't know if "cool" has recently been redefined, because RP is clearly not cool in any world I've visited recently. But ho hum...
Adrian Chiles - semi-professional Brummie - defends his accent here, while more serious news outlets give the story a different slant here, here and here.
ENA5 - Language Variation
ENGA3 - Language Explorations