[TYPO3] Indexed Search: UTF-8 conversion causing problems

[Gavin Frayne]

--> Typo3 4.0
--> Indexed Search 2.9.0

Special characters on pages are being garbled by the function 
charsetEntity2utf8 in class.indexer.php.

e.g. HTML Text = Jörg, Search result content = Jörg

Strangely enough, searching for "jörg" will return the correct page, even 
though the result content is garbled.

By commenting out the calls to the function charsetEntity2utf8, this 
process is reversed i.e. the characters are displayed correctly,
but searching for "jörg" returns nothing.

I'm not using any extensions that extend the indexed search plugin i.e. 
there are no XCLASSes to any indexed_search file (no BE[XCLASS]
or FE[XCLASS] entries in $TYPO3_CONF_VARS).

I've set the following in TS:
page.config.metaCharset = ISO-8859-15
page.config.renderCharset = ISO-8859-15
language = en
doctype = xhtml_trans
xhtml_cleaning = all
config.htmlTag_langKey = en

Has anyone got some insight into some settings that may be wrong/missing 
or any ideas about how to update the charsetEntity2utf8 funtion
to stop this garbled output?

Regards,
Gavin