Outputing & Not & not the usual problem!

I am trying to output a text file .xls (tab). One of the colums is a URL with a querystring with several parameters.

It should look like the following "http://www.site.co.uk/index.asp?sr=1005&du=10001_something"

However I get "http://www.site.co.uk/index.asp?sr=1005&du=10001_something"

Below is the xsl...

Output section...
<xslutput method="html" omit-xml-declaration="yes" indent="no" encoding="iso-8859-1"/>

Problem section...
<xsl:text>http://www.site.co.uk/index.asp?sr=</xsl:text>
<xsl:text>1005</xsl:text><!--Live Source-->
<xsl:text disable-output-escaping="yes">&</xsl:text>
<xsl:text>du=</xsl:text>
<xsl:text>10001_</xsl:text>
<xsl:value-of select="XSL_Ext:get_Trackable_URL(4,@ItemKey,@ChildItemKey,0,0)"/>
<xsl:text>&sep;</xsl:text>
<xsl:text>URL Image</xsl:text>
<xsl:text>
</xsl:text>

I have tried "&" and "&#x0026" all with disable-output-escaping (d-o-e) set at "yes" and "no" both output "&". I have also set the output type to text, html and xml all with the same effect.

Can any one suggest anything else?

All doc types are encoding="iso-8859-1" and I am using XslTransform in .Net.