Outputting data in UTF-8

We are sending XML to a 3rd party on request and this is being delivered from a 9iR2 database running on Solaris and using Oracle HTTP server and mod_plsql.

The 3rd party has told us that the data should be in UTF-8 encoding instead of ISO-8859-1

I had assumed (naively it appears) that simply setting the http headers and document declaration e.g.:

  owa_util.mime_header('text/xml; charset=UTF-8', false);   owa_util.http_header_close;
  htp.p('<?xml version="1.0" encoding="UTF-8"?>');

would be sufficient however when looking in e.g. firefox at the document details it still says that the encoidng is ISO-8859-1

So the question is: how can I generate the data using the requested encoding?

Is there an 'alter session' directive I can use?

Thanks.....

-- 

jeremy