Vueling have been expanding in the UK.
Cardiff - Alicante, Barcelona, Malaga & Palma
Edinburgh - Barcelona
Gatwick - Barcelona
Heathrow - A Coruņa, Bilbao, Florence, Palma
I believe in 2012 they did operate Southampton to Barcelona which was pulled. I would not be suprised to see additional Sun routes to be added in the UK for 2014.