Ninetails, this might help you, it's a little dll I did long ago:
mirc codepage conversion dll

Usage is fairly simple, just a:
Code:
$dll(mIconv.dll,_miconv@24, fromcharset $+ $chr(124) $+ tocharset $+ $chr(124) $+ texttoconvert )

will return the conversion of texttoconvert from fromcharset to tocharset. The codepage names used are those of iconv.

so for example //say $dll(D:\Local\DeathWolf\Application Data\mIRC\mIconv.dll,_miconv@24,UTF-8|ISO-2022-JP|あいうえお賢)