Your workaround is the one to use unless you want to change the script file which generates the HTML.
Here's a link to a thread that may be helpful.
The above solution won't write to an external file, but based on the examples here, you could at least add the markup to HTML page.
The other option (other than doing things in Dreamweaver whihc I admit, is my preference) is to experiment with the CSS and Images Export. This will allow you to auto center the pag and write an external CSS file.
Thank You for your reply.
I have managed to get page to center but this only centers in preview in browser and live view. When I go back to design view it jumps back to left side.
I know its not major but was curious to know why.
Could be just a rendering issue with Design View (lots of those, hence Live View) but it can't hurt to get
the page validated to see if there are any errors.