The number is like this: 8210 3xxx xxxx
I've found out that the 82 is the Korean in code, so presume that the mobile number must start 010 and the leading 0 has been left off, which is also correct according to the rules of sending SMS to any other country.
I have added the + symbol to the start of the number, or in other words the UK out code i.e. 00.
The SMS doesn't go through, at least it sends but is not received.
Has anyone got any ideas?