You can create a new div which to contains all the report body.

Then you can add the following in the div: style="top:50px" and the body div should go down.

Hope that helps you! :)

Juan.

You could also try fiddling with the Header Spacing and Top Margin options in the Settings > Reports > Paper Format. Increasing Header Spacing would probably help push the body down

I also think the best way is to do it with the Paper Format. I usually create a new paperformat.xml in the data folder of my custom module. There you can inherit the record, so you don't have to change it by hand and it will stay the same no matter where you install your custom module:

<record id="report.paperformat_euro" model="report.paperformat">
     <field name="margin_top">50</field>
     <field name="margin_bottom">40</field>
     <field name="margin_left">7</field>
     <field name="margin_right">7</field>
     <field name="header_spacing">45</field>
 </record>