Exporting complex HTML table to Excel

I want to export an HTML table to excel sheet.
I would have done this with CVS format if I didn't have to keep some formatting and add pictures.

I have tries using the Office 2003 XML format for that, i.e.

<?xml version="1.0"?>
<?mso-application progid="Excel.Sheet"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
          xmlns:o="urn:schemas-microsoft-com:office:office"
          xmlns:x="urn:schemas-microsoft-com:office:excel"
          xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
          xmlns:html="http://www.w3.org/TR/REC-html40">
    <DocumentProperties xmlns="urn:schemas-microsoft-com:office:office">
    ...
    </DocumentProperties>
    <OfficeDocumentSettings xmlns="urn:schemas-microsoft-com:office:office">
    ...
    </OfficeDocumentSettings>
    <ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel">
    ...
    </ExcelWorkbook>
    <Styles>...</Styles>
    <Worksheet ss:Name="Sheet1">...</Worksheet>
</Workbook>

And then some JavaScript code to "download" it using data URI and

'data:application/vnd.ms-excel;charset=utf-8, '+
 encodeURIComponent(STRING_XML_REPRESENTATION));

I have 2 problems:

1. The document saved as xls (or xlsx) opens fine on OpeOffice \ LibreOffice but throws an error on Excel, and
2. I do not seem to find a way to add images to the file.

I do not want to save it as an xml file since opening it defaults to a web browser in most cases.