One thing you could try is to dump, 'search and replace' in an editor and import again.
However problems that may occur are:
1) dump may be too big for an editor (take one table at a time). I know that Ultraedit for instance handles very big files without being unacceptable slow.
2) if you have binary data (BLOBs) then
* such characters may occur in the textual display of such BLOB so here you should not 'search and replace' them of course.
* some editors may garble HEX patterns that are not valid UTF8. With SQLyog Enterprise/Ultimate the 'scheduled backup' has an option to set the encoding of the dump. Make it latin1 (ANSI) for this special purpose – not utf8, as all HEX patterns are valid in ANSI.
* some editors may truncate long BLOB/TEXT/bulk inserts
— so be careful – do not drop the original tables before you are sure that it is OK! For instance you could 'duplicate table', next export-edit-import the duplicate. Now rename the original and rename the duplicate to the original name.
