I hope you find a specific subject you'd like to work on, though I don't doubt you will ^^
Have you? I visited S. Korea myself last summer and have been self-studying it too for a couple of years now, so I can completely understand your wish to deepen that, see for yourself what you've covered and what you've missed etc., I'm thinking of taking an advanced TOPIK test to see how I fare, maybe while in Korea. Do you know what level in Korean the MA is supposed to take you to?
I'm not sure to be honest, I like it all so it will be hard to decide.. Maybe applied linguistics first then move on to a PhD later on.. I just don't think I'm ready yet. I'm really interested in Child Language Acquisition so first hand observation through experience teaching multilingual children could also be an asset on the long run, maybe? So long as I actually record and study the children's linguistic behaviour the way I have seen my undergrad teacher do? Then again I might just be fooling myself, but I do think I need some 'field experience'.
So you'd be teaching English on an E2 for a while in Korea then you'd go back to study in the UK?