Im currently living in UK. I need to send packages (one is over 10kg, otherone is around 1.5kg) to S.Korea.
But Post office in UK charge so much, 1.5kg is around 34pounds. 10Kg one is 177pounds..

I really don't care how long it will take. My concern is the prise and safe deliver.

TBH, you are unlikely to find a cheaper method.

Are these prices for surface mail as opposed to air mail ?