I recommend you stick to something similar to the pagelayout used for the printed version of the page that comes with ez "print_pagelayout.tpl".
I am working in a similar problem exporting (saving somehow) the content of the information of the basket to an excel format, the only problem is that I have to have images, but images are not constrain into a cell (everybody seems to say the same), so it's getting a little difficult to solve this issue.
Diseño Web Cuba
Web Design Cuba
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# Consists of groups which are the layout name
# A layout group can have the followin variables
# - PageLayout - Uses a different pagelayout for this page
# - ContentType - Sets 'Content-Type' for layout module output
# example: ContentType=text/xml
I don't know what 'ou' means, but I've successfully used this library:
http://www.phpexcel.net (PHPExcel)
This is much better than just trying to force headers...
Good luck, Piotrek