Other countries send their chart-topping acts to the Eurovision Song Contest but most 'big name' bands in the UK probably wouldn't want to have anything to do with the competition.
That's partly because the UK regards the competition as 'a bit of a joke', meaning that it wouldn't do much for the 'street cred' of a band who agreed to perform.
Possibly more so, however, it's to do with the fact that many of our most successful artists only perform their own music. (Can you imagine Elton John agreeing to represent the UK if he was forced to sing songs written by inferior writers?).
So, to give the UK the same chance of winning as other countries have, the BBC has decided to go for a 'big name' group performing their own material.
http://www.bbc.co.uk/...nouncement_2011.shtml
Chris