Am I able to buy electronics in Seoul airport duty free as a transit passenger? and is it cheaper than the UK?

I am travelling from UK to New Zealand, and transiting in Seoul airport for a few hours on the way. I really want a new mobile phone and digital camera before I go to New Zealand, and want to know if a) I'll be able to access the duty free shops as a transit passenger, and b) If it's going to be cheaper than the deals in the UK. EG a Sony Ericcson 750i phone for 拢89.00

Don't forget you only have a certain amount that is duty free