For flights around £500 try the following airlines:
http://www.emirates.com/kr/english/ Who have been recommended, as you get to fly in the new Airbus A380, which is a bit nicer than a Boing 747!
http://www.qatarairways.com/uk/en/homepage.html for Qatar, with a bit of a longer stopover for a connecting Qatar flight out of Doha to Seoul.
http://www.finnair.com/finnaircom/wps/portal/travel/en_UK?fromjump=true&locale=en_UK for Finnair, with a short stopover in Helsinki-Vantaa airport.

After that the prices start to rise. For upwards of £600:
http://www.klm.com/travel/gb_en/index.htm for KLM, Royal Dutch Airlines.
http://www.koreanair.com/ for Korean air, who quote their flight prices in Euro's.

Hope to see you all there!!
Pil Suhng!

Master Cassar