I had an experience with a Korean WG whilst in NZ that I rather enjoyed. Shame I wasn't staying long in that part of NZ.
On that note, I've noticed though you don't seem to get many Koreans WG in the UK (maybe I'm not looking hard enough?)
Koreans aren't well acquainted with the UK or the idea of living there.
The best Korean girls stay in Korea due to the sheer number of punters in the country. The best of the rest rest work in Japan, China, Hong Kong, Singapore etc.
The rest move on to Australia, NZ, USA, Canada.
There is a growing number of Koreans taking an interest in Europe these days though. After Germany, the UK is probably the second most popular European destination.
Sadly, Koreans are just nationalistic and xenophobic as their cousins across the sea of Japan (a generalisation, yes I know) - meaning most Korean WGs in the UK are for Korean punters only.
They have their own portals which they operate from, and because virtually less than 1% of UK punters know/understand the language, it is practically impossible to find them.
Every once in a while a K-girl slips through the net onto Adultwork and in parlours, but they are drops compared to the ocean of Korean WGs out there.